51
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Nielsen JH, Simesen P, Bisgaard CZ, Stapelfeldt H, Filsinger F, Friedrich B, Meijer G, Küpper J. Stark-selected beam of ground-state OCS molecules characterized by revivals of impulsive alignment. Phys Chem Chem Phys 2011; 13:18971-5. [DOI: 10.1039/c1cp21143a] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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52
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Filsinger F, Meijer G, Stapelfeldt H, Chapman HN, Küpper J. State- and conformer-selected beams of aligned and oriented molecules for ultrafast diffraction studies. Phys Chem Chem Phys 2010; 13:2076-87. [PMID: 21165481 DOI: 10.1039/c0cp01585g] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The manipulation of the motion of neutral molecules with electric or magnetic fields has seen tremendous progress over the last decade. Recently, these techniques have been extended to the manipulation of large and complex molecules. In this article we introduce experimental approaches to the manipulation of large molecules, i.e., the deflection, focusing and deceleration using electric fields. We detail how these methods can be exploited to spatially separate quantum states and how to select individual conformers of complex molecules. We briefly describe mixed-field orientation experiments made possible by the quantum-state selection. Moreover, we provide an outlook on ultrafast diffraction experiments using these highly controlled samples.
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Affiliation(s)
- Frank Filsinger
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
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53
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Ohshima Y, Hasegawa H. Coherent rotational excitation by intense nonresonant laser fields. INT REV PHYS CHEM 2010. [DOI: 10.1080/0144235x.2010.511769] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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54
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Shu CC, Yuan KJ, Hu WH, Cong SL. Field-free molecular orientation with terahertz few-cycle pulses. J Chem Phys 2010; 132:244311. [PMID: 20590197 DOI: 10.1063/1.3458913] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Chuan-Cun Shu
- Department of Physics, Dalian University of Technology, Dalian 116024, China.
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55
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Irimia D, Janssen MHM. Toward elucidating the mechanism of femtosecond pulse shaping control in photodynamics of molecules by velocity map photoelectron and ion imaging. J Chem Phys 2010; 132:234302. [DOI: 10.1063/1.3436720] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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56
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Rakitzis TP, Janssen MH. Photofragment angular momentum distributions from oriented and aligned polyatomic molecules: beyond the axial recoil limit. Mol Phys 2010. [DOI: 10.1080/00268970903580158] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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57
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Wu C, Zeng G, Jiang H, Gao Y, Xu N, Gong Q. Molecular rotational excitation by strong femtosecond laser pulses. J Phys Chem A 2009; 113:10610-8. [PMID: 19746946 DOI: 10.1021/jp905743v] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We study the rotational wave packet created by nonadiabatic rotational excitation of molecules with strong femtosecond laser pulses. The applicable condition of the Delta-Kick method is obtained by comparing the laser intensity and pulse duration dependences of the wave packet calculated with different methods. The wave packet evolution is traced analytically with the Delta-Kick method. The calculations demonstrate that the rotational populations can be controlled for the rotational wave packet created by two femtosecond laser pulses. The evolution of the rotational wave packet with controlled populations produces interference patterns with exotic spatial symmetries. These calculations are validated by comparing the theoretical calculations with our experimental measurements for the rotational wave packet created by thermal ensemble CO(2) and two strong femtosecond laser pulses. Potential applications in molecular science are also discussed for the rotational wave packet with controlled populations and spatial symmetries.
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Affiliation(s)
- Chengyin Wu
- State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, People's Republic of China.
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58
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Hu WH, Shu CC, Han YC, Yuan KJ, Cong SL. Efficient enhancement of field-free molecular orientation by combining terahertz few-cycle pulses and rovibrational pre-excitation. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.09.051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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59
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Chichinin AI, Gericke KH, Kauczok S, Maul C. Imaging chemical reactions – 3D velocity mapping. INT REV PHYS CHEM 2009. [DOI: 10.1080/01442350903235045] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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60
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Wu C, Zeng G, Gao Y, Xu N, Peng LY, Jiang H, Gong Q. Controlling molecular rotational population by wave-packet interference. J Chem Phys 2009; 130:231102. [DOI: 10.1063/1.3155063] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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61
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Bisgaard CZ, Clarkin OJ, Wu G, Lee AMD, Gessner O, Hayden CC, Stolow A. Time-Resolved Molecular Frame Dynamics of Fixed-in-Space CS2 Molecules. Science 2009; 323:1464-8. [DOI: 10.1126/science.1169183] [Citation(s) in RCA: 271] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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62
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Filsinger F, Küpper J, Meijer G, Holmegaard L, Nielsen JH, Nevo I, Hansen JL, Stapelfeldt H. Quantum-state selection, alignment, and orientation of large molecules using static electric and laser fields. J Chem Phys 2009; 131:064309. [DOI: 10.1063/1.3194287] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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63
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Hasegawa H, Ohshima Y. Quantum state reconstruction of a rotational wave packet created by a nonresonant intense femtosecond laser field. PHYSICAL REVIEW LETTERS 2008; 101:053002. [PMID: 18764388 DOI: 10.1103/physrevlett.101.053002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2008] [Indexed: 05/26/2023]
Abstract
We have experimentally determined the amplitudes and phases of a rotational wave packet in an adiabatically cooled benzene molecule, created by a nonresonant intense femtosecond laser field. In this wave-packet reconstruction, the initial wave packet is further interfered by a replica of the first laser pulse, and the resultant modulation in population is observed in a state-resolved manner. Though several states with different nuclear-spin modifications are populated in the initial condition, a single wave packet created from one of them (with J=0) is specifically reconstructed. Phase shifts characteristic of stepwise Raman excitation beyond the perturbative regime are experimentally identified.
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Affiliation(s)
- Hirokazu Hasegawa
- Institute for Molecular Science, National Institutes of Natural Sciences, Myodaiji, Okazaki, Japan
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64
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Tscherbul TV. Differential scattering of cold molecules in superimposed electric and magnetic fields. J Chem Phys 2008; 128:244305. [DOI: 10.1063/1.2943197] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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65
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Radenović DČ, van Roij AJ, Wu SM, Ter Meulen J, Parker DH, van der Loo MP, Janssen LM, Groenenboom GC. Photodissociation of vibrationally excited OH/OD radicals. Mol Phys 2008. [DOI: 10.1080/00268970801922783] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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66
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Brouard M, Green AV, Quadrini F, Vallance C. Photodissociation dynamics of OCS at 248nm: The S(D21) atomic angular momentum polarization. J Chem Phys 2007; 127:084304. [PMID: 17764245 DOI: 10.1063/1.2757618] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The dissociation of OCS has been investigated subsequent to excitation at 248 nm. Speed distributions, speed dependent translational anisotropy parameters, angular momentum alignment, and orientation are reported for the channel leading to S((1)D(2)). In agreement with previous experiments, two product speed regimes have been identified, correlating with differing degrees of rotational excitation in the CO coproducts. The velocity dependence of the translational anisotropy is also shown to be in agreement with previous work. However, contrary to previous interpretations, the speed dependence is shown to primarily reflect the effects of nonaxial recoil and to be consistent with predominant excitation to the 2 (1)A(') electronic state. It is proposed that the associated electronic transition moment is polarized in the molecular plane, at an angle greater than approximately 60 degrees to the initial linear OCS axis. The atomic angular momentum polarization data are interpreted in terms of a simple long-range interaction model to help identify likely surfaces populated during dissociation. Although the model neglects coherence between surfaces, the polarization data are shown to be consistent with the proposed dissociation mechanisms for the two product speed regimes. Large values for the low and high rank in-plane orientation parameters are reported. These are believed to be the first example of a polyatomic system where these effects are found to be of the same order of magnitude as the angular momentum alignment.
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Affiliation(s)
- M Brouard
- The Physical and Theoretical Chemistry Laboratory, The Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
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67
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Zou S, Balint-Kurti GG, Manby FR. Vibrationally selective optimal control of alignment and orientation using infrared laser pulses: application to carbon monoxide. J Chem Phys 2007; 127:044107. [PMID: 17672681 DOI: 10.1063/1.2748400] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Optimal control methods are used to study molecular alignment and orientation using infrared laser pulses. High order molecule-field interactions are taken into account through the use of the electric-nuclear Born-Oppenheimer approximation [G. G. Balint-Kurti et al., J. Chem. Phys. 122, 084110 (2005)]. High degrees of alignment and orientation are achieved by optimized infrared laser pulses of duration on the order of one rotational period of the molecule. It is shown that, through the incorporation of a vibrational projection operator into the optimization procedure, it is possible not only to maximize the alignment and orientation but also to bring the whole system into a single prescribed vibrational manifold. Numerical calculations are performed for carbon monoxide using ab initio potential energies computed in the presence of external electric fields.
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Affiliation(s)
- Shiyang Zou
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom.
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68
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Lipciuc ML, Janssen MHM. Slice imaging of the quantum state-to-state cross section for photodissociation of state-selected rovibrational bending states of OCS (v2=0,1,2∣JlM)+hν→CO(J)+S(D21). J Chem Phys 2007; 126:194318. [PMID: 17523815 DOI: 10.1063/1.2737450] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using hexapole quantum state-selection of OCS (v(2)=0,1,2/JlM) and high-resolution slice imaging of quantum state-selected CO(J), the state-to-state cross section OCS (v(2)=0,1,2/JlM)+hnu-->CO(J)+S((1)D(2)) was measured for bending states up to v(2)=2. The population density of the state-selected OCS (v(2)=0,1,2 /JlM) in the molecular beam was obtained by resonantly enhanced multiphoton ionization of OCS and comparison with room temperature bulk gas. A strong increase of the cross section with increasing bending state is observed for CO(J) in the high J region, J=60-67. Integrating over all J states the authors find sigma(v(2)=0):sigma(v(2)=1):sigma(v(2)=2)=1.0:7.0:15.0. A quantitative comparison is made with the dependence of the transition dipole moment function on the bending angle.
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Affiliation(s)
- M Laura Lipciuc
- Department of Chemistry, Laser Centre, Vrije Universiteit, de Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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69
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Lim IS, Lim JS, Lee YS, Kim SK. Experimental and theoretical study of the photodissociation reaction of thiophenol at 243nm: Intramolecular orbital alignment of the phenylthiyl radical. J Chem Phys 2007; 126:034306. [PMID: 17249870 DOI: 10.1063/1.2424939] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The photoinduced hydrogen (or deuterium) detachment reaction of thiophenol (C(6)H(5)SH) or thiophenol-d(1) (C(6)H(5)SD) pumped at 243 nm has been investigated using the H (D) ion velocity map imaging technique. Photodissociation products, corresponding to the two distinct and anisotropic rings observed in the H (or D) ion images, are identified as the two lowest electronic states of phenylthiyl radical (C(6)H(5)S). Ab initio calculations show that the singly occupied molecular orbital of the phenylthiyl radical is localized on the sulfur atom and it is oriented either perpendicular or parallel to the molecular plane for the ground (B(1)) and the first excited state (B(2)) species, respectively. The experimental energy separation between these two states is 2600+/-200 cm(-1) in excellent agreement with the authors' theoretical prediction of 2674 cm(-1) at the CASPT2 level. The experimental anisotropy parameter (beta) of -1.0+/-0.05 at the large translational energy of D from the C(6)H(5)SD dissociation indicates that the transition dipole moment associated with this optical transition at 243 nm is perpendicular to the dissociating S-D bond, which in turn suggests an ultrafast D+C(6)H(5)S(B(1)) dissociation channel on a repulsive potential energy surface. The reduced anisotropy parameter of -0.76+/-0.04 observed at the smaller translational energy of D suggests that the D+C(6)H(5)S(B(2)) channel may proceed on adiabatic reaction paths resulting from the coupling of the initially excited state to other low-lying electronic states encountered along the reaction coordinate. Detailed high level ab initio calculations adopting multireference wave functions reveal that the C(6)H(5)S(B(1)) channel may be directly accessed via a (1)(n(pi),sigma(*)) photoexcitation at 243 nm while the key feature of the photodissociation dynamics of the C(6)H(5)S(B(2)) channel is the involvement of the (3)(n(pi),pi(*))-->(3)(n(sigma),sigma(*)) profile as well as the spin-orbit induced avoided crossing between the ground and the (3)(n(pi),sigma(*)) state. The S-D bond dissociation energy of thiophenol-d(1) is accurately estimated to be D(0)=79.6+/-0.3 kcalmol. The S-H bond dissociation energy is also estimated to give D(0)=76.8+/-0.3 kcalmol, which is smaller than previously reported ones by at least 2 kcalmol. The C-H bond of the benzene moiety is found to give rise to the H fragment. Ring opening reactions induced by the pi-pi(*)n(pi)-pi(*) transitions followed by internal conversion may be responsible for the isotropic broad translational energy distribution of fragments.
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Affiliation(s)
- Ivan S Lim
- Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
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70
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Schwabe C. Chemistry and biodiversity. Chem Biodivers 2006; 1:1584-8. [PMID: 17191802 DOI: 10.1002/cbdv.200490119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Complex structures produced by noncatalyzed multi-step chemical processes must have highly probable origins and assembly routes. Within any frame of reference, life is easily the most-complex self-assembled structure known to man. It is not possible to calculate a finite time for biogenesis by statistical mechanics, but the abundance of life makes it reasonable to propose an accelerating principle of nature that naturally shortened the time for cell formation to a billion years or less. This hypothetical principle, which I have called valence-orbital bias, is thought to be responsible for the discrepancy between statistics and observation, and carries with it, as a conditio sine qua non, multiple origins of life.The new concept resolves the differences between the predictions based on statistical mechanics and the relatively rapid appearance of life during the post-accretion period. It suggests as well that species and variants, the units of propagation, may also have been the units of evolution. Produced in profusion by chemistry, the origins are culled by natural selection, whereby failure means extinction, not adaptation. Biodiversity, thus, becomes a direct consequence of chemistry without positive feedback from the environment and without a constructive role for mutation.
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Affiliation(s)
- Christian Schwabe
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA.
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71
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Lee SK, Silva R, Thamanna S, Vasyutinskii OS, Suits AG. S(D21) atomic orbital polarization in the photodissociation of OCS at 193nm: Construction of the complete density matrix. J Chem Phys 2006; 125:144318. [PMID: 17042601 DOI: 10.1063/1.2357948] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The absolute velocity-dependent alignment and orientation for S(1D2) atoms from the photodissociation of OCS at 193 nm were measured using the dc slice imaging method. Three main peaks ascribed to specific groups of high rotational levels of CO in the vibrational ground state were found, with rotationally resolved rings in a fourth slow region ascribed to weak signals associated with excited vibrational states of CO. The observed speed-dependent beta and polarization parameters support the interpretation that there are two main dissociation processes: a simultaneous two-surface (A' and A") excitation and the initial single-surface (A') excitation followed by the nonadiabatic crossing to ground state. At 193 nm photodissociation, the nonadiabatic dissociation process is strongly enhanced relative to longer wavelengths. The angle- and speed-dependent S(1D2) density matrix can be constructed including the higher order (K = 3,4) contributions for the circularly polarized dissociation light. This was explicitly done for selected energies and angles. It was found in one case that the density matrix is sensitively affected by the rank 4 terms, suggesting that the higher order contributions should not be overlooked for an accurate picture of the dissociation dynamics in this system.
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Affiliation(s)
- Suk Kyoung Lee
- Department of Chemistry, Wayne State Univeristy, Detroit, Michigan 48202, USA
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72
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Gijsbertsen A, Linnartz H, Stolte S. Parity-dependent rotational rainbows in D2–NO and He–NO differential collision cross sections. J Chem Phys 2006; 125:133112. [PMID: 17029438 DOI: 10.1063/1.2234771] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The (j', Omega', epsilon') dependent differential collision cross sections of D2 with fully state selected (j = 12, Omega = 12, epsilon = -1) NO have been determined at a collision energy of about 550 cm(-1). The collisionally excited NO molecules are detected by (1+1') resonance enhanced multiphoton ionization combined using velocity-mapped ion-imaging. The results are compared to He-NO scattering results and tend to be more forward scattered for the same final rotational state. Both for collisions of the atomic He and the molecular D2 with NO, scattering into pairs of rotational states with the same value of n = j' - epsilon epsilon'2 yields the same angular dependence of the cross section. This "parity propensity rule" remains present both for spin-orbit conserving and spin-orbit changing transitions. The maxima in the differential cross sections-that reflect rotational rainbows-have been extracted from the D2-NO and the He-NO differential cross sections. These maxima are found to be distinct for odd and even parity pair number n. Rainbow positions of parity changing transitions (n is odd) occur at larger scattering angles than those of parity conserving transitions (n is even). Parity conserving transitions exhibit-from a classical point of view-a larger effective eccentricity of the shell. No rainbow doubling due to collisions onto either the N-end or the O-end was observed. From a classical point of view the presence of a double rainbow is expected. Rotational excitation of the D2 molecules has not been observed.
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Affiliation(s)
- Arjan Gijsbertsen
- Laser Centre and Department of Physical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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73
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Lim JS, Lim IS, Lee KS, Ahn DS, Lee YS, Kim SK. Intramolecular Orbital Alignment Observed in the Photodissociation of [D1]Thiophenol. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200601985] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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74
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Lim JS, Lim IS, Lee KS, Ahn DS, Lee YS, Kim SK. Intramolecular Orbital Alignment Observed in the Photodissociation of [D1]Thiophenol. Angew Chem Int Ed Engl 2006; 45:6290-3. [PMID: 16960908 DOI: 10.1002/anie.200601985] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Jeong Sik Lim
- Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology (KAIST), Daejoen 305-701, Republic of Korea
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75
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Gilijamse JJ, Hoekstra S, van de Meerakker SYT, Groenenboom GC, Meijer G. Near-Threshold Inelastic Collisions Using Molecular Beams with a Tunable Velocity. Science 2006; 313:1617-20. [PMID: 16973875 DOI: 10.1126/science.1131867] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Molecular scattering behavior has generally proven difficult to study at low collision energies. We formed a molecular beam of OH radicals with a narrow velocity distribution and a tunable absolute velocity by passing the beam through a Stark decelerator. The transition probabilities for inelastic scattering of the OH radicals with Xe atoms were measured as a function of the collision energy in the range of 50 to 400 wavenumbers, with an overall energy resolution of about 13 wavenumbers. The behavior of the cross-sections for inelastic scattering near the energetic thresholds was accurately measured, and excellent agreement was obtained with cross-sections derived from coupled-channel calculations on ab initio computed potential energy surfaces.
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Affiliation(s)
- Joop J Gilijamse
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
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76
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Ohmura H, Saito N, Tachiya M. Selective ionization of oriented nonpolar molecules with asymmetric structure by phase-controlled two-color laser fields. PHYSICAL REVIEW LETTERS 2006; 96:173001. [PMID: 16712292 DOI: 10.1103/physrevlett.96.173001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Indexed: 05/09/2023]
Abstract
We report on the selective ionization of oriented nonpolar molecules with asymmetric structure by using phase-controlled two-color omega + 2omega laser pulses with an intensity of 1.0 x 10(13) W/cm(2) (tunneling ionization regime) and a pulse duration of 130 fs. The orientation of 1-bromo-2-chloroethane was monitored by the directional asymmetries of the forward-backward emission in dissociative ionization. The observed direction of orientation clearly confirms that molecular orientation is induced not by dynamic orientation but by selective ionization of oriented molecules, which reflects the structure of the highest occupied molecular orbital. This method can be applied for the vast majority of molecules.
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Affiliation(s)
- Hideki Ohmura
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
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77
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Abstract
▪ Abstract The motion of polar molecules can be controlled by time-varying inhomogeneous electric fields. In a Stark decelerator, this is exploited to accelerate, transport, or decelerate a fraction of a molecular beam. When combined with a trap, the decelerator provides a means to store the molecules for times up to seconds. Here, we review our efforts to produce cold molecules via this technique. In particular, we present a new generation Stark decelerator and electrostatic trap that selects a significant part of a molecular beam pulse that can be loaded into the trap. Deceleration and trapping experiments using a beam of OH radicals are discussed.
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78
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Gessner O, Lee AMD, Shaffer JP, Reisler H, Levchenko SV, Krylov AI, Underwood JG, Shi H, East ALL, Wardlaw DM, Chrysostom ETH, Hayden CC, Stolow A. Femtosecond Multidimensional Imaging of a Molecular Dissociation. Science 2006; 311:219-22. [PMID: 16357226 DOI: 10.1126/science.1120779] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The coupled electronic and vibrational motions governing chemical processes are best viewed from the molecule's point of view-the molecular frame. Measurements made in the laboratory frame often conceal information because of the random orientations the molecule can take. We used a combination of time-resolved photoelectron spectroscopy, multidimensional coincidence imaging spectroscopy, and ab initio computation to trace a complete reactant-to-product pathway-the photodissociation of the nitric oxide dimer-from the molecule's point of view, on the femtosecond time scale. This method revealed an elusive photochemical process involving intermediate electronic configurations.
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Affiliation(s)
- O Gessner
- Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, Ontario K1A 0R6, Canada
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79
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Laura Lipciuc M, Janssen MHM. Slice imaging of quantum state-to-state photodissociation dynamics of OCS. Phys Chem Chem Phys 2006; 8:3007-16. [PMID: 16880914 DOI: 10.1039/b605108a] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Slice imaging experiments are reported for the quantum state-to-state photodissociation dynamics of OCS. Both one-laser and two-laser experiments are presented detecting CO(J) or S((1)D(2)) photofragments from the dissociation of hexapole state-selected OCS(v(2) = 0,1,2 / J = 1,2) molecules. We present data using our recently developed large frame CCD centroiding detector and have implemented a new high speed MCP high voltage pulser with an effective slice width of only 6 ns. Slice images are presented for quantum state-to-state photolysis, near 230 nm, of vibrationally excited OCS(v(2) = 0,1,2). Two-laser pump-probe experiments detecting CO(J = 63 or 64) show a dramatic change in the beta parameter for the same final state of CO(J) when the photolysis energy is reduced by about 1000 cm(-1). We attribute the observed change from large positive to large negative beta to a large increase of the molecular frame deflection angle at very slow recoil velocity, due to a breakdown of the axial recoil. Two-laser experiments on the S((1)D(2)) fragment reveal single well-separated rings in the slice images correlating with individual CO(J) states. Strong polarization effects of the probe laser are observed, both in the angular distribution of the intensity of single S((1)D(2)) rings and in the resolution of the radial velocity distribution. It is shown how the broadening of the velocity distribution can be reduced by a directed ejection of the electron in the ionization process perpendicular to the slice imaging plane. The dissociation energy of OCS(v(2) = 0, J = 0) --> CO(J = 0) + S((1)D(2)) is determined with high accuracy D(0) = (34 608 +/- 24) cm(-1).
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Affiliation(s)
- M Laura Lipciuc
- Laser Centre and Department of Chemistry, Vrije Universiteit, de Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands
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80
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Ashfold MNR, Nahler NH, Orr-Ewing AJ, Vieuxmaire OPJ, Toomes RL, Kitsopoulos TN, Garcia IA, Chestakov DA, Wu SM, Parker DH. Imaging the dynamics of gas phase reactions. Phys Chem Chem Phys 2006; 8:26-53. [PMID: 16482242 DOI: 10.1039/b509304j] [Citation(s) in RCA: 240] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ion imaging methods are making ever greater impact on studies of gas phase molecular reaction dynamics. This article traces the evolution of the technique, highlights some of the more important breakthroughs with regards to improving image resolution and in image processing and analysis methods, and then proceeds to illustrate some of the many applications to which the technique is now being applied--most notably in studies of molecular photodissociation and of bimolecular reaction dynamics.
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81
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Roeterdink WG, Rijs AM, Janssen MHM. Imaging of Ultrafast Molecular Elimination Reactions. J Am Chem Soc 2005; 128:576-80. [PMID: 16402845 DOI: 10.1021/ja055658x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ultrafast molecular elimination reactions are studied using the velocity map ion imaging technique in combination with femtosecond pump-probe laser excitation. A pump laser is used to initiate the dissociative reaction, and after a predetermined time delay a probe laser "interrogates" the molecular system. Ionic fragments are detected with a two-dimensional velocity map imaging detector providing detailed information about the energetic and vectorial properties of mass selected photofragments. In this paper we discuss the ultrafast elimination of molecular iodine, I(2), from IF(2)C-CF(2)I, where the iodine atoms originate from neighboring carbon atoms. By varying the femtosecond delay between pump and probe pulse, it is found that elimination of molecular iodine is a concerted process, although the two carbon-iodine bonds are not broken synchronously. Energetic considerations suggest that the crucial step in this fragmentation process is an electron transfer between the two iodine atoms in the parent molecule, which leads to Coulombic attraction and the creation of an ion-pair state in the molecular iodine fragment.
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Affiliation(s)
- Wim G Roeterdink
- Laser Centre and Department of Chemistry, Vrije Universiteit de Boelelaan 1083, Amsterdam, The Netherlands
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82
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Gijsbertsen A, Linnartz H, Rus G, Wiskerke AE, Stolte S, Chandler DW, Kłos J. Differential cross sections for collisions of hexapole state-selected NO with He. J Chem Phys 2005; 123:224305. [PMID: 16375474 DOI: 10.1063/1.2126969] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The first measurements of differential inelastic collision cross sections of fully state-selected NO (j=12, Omega=12, epsilon= -1) with He are presented. Full state selection is achieved by a 2 m long hexapole, which allows for a systematic study of the effect of parity conservation and breaking on the differential cross section. The collisionally excited NO molecules are detected using a resonant (1+1') REMPI ionization scheme in combination with the velocity-mapped, ion-imaging technique. The current experimental configuration minimizes the contribution of noncolliding NO molecules in other rotational states j, Omega, epsilon--that contaminates images--and allows for study of the collision process at an unprecedented level of detail. A simple method to correct ion images for collision-induced alignment is presented as well and its performance is demonstrated. The present results show a significant difference between differential cross sections for scattering into the upper and lower component of the Lambda-doublet of NO. This result cannot be due to the energy splitting between these components.
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Affiliation(s)
- A Gijsbertsen
- Laser Centre and Department of Physical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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83
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Wang ZS. Optimally controlled optomechanical work cycle for a molecular locomotive. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2005; 17:S3767-S3782. [PMID: 21690723 DOI: 10.1088/0953-8984/17/47/009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This work seeks to apply the laser optimal control technique to light-driven molecular motors. Taking a recently proposed molecular locomotive as a model system, a control loop is developed specifically for it, and concrete schemes for experimentally closing the loop are devised. A list of unique control objectives is rigorously formulated from the nanomachinery perspective, and corresponding optimization is made feasible by an innovative application of the established technique of closed-loop learning control. The optimization may be pursued for individual laser operational steps as well as for the overall nanolocomotion performance of the entire work cycle. The locomotive optimal control, capable of co-adapting the laser procedure and the periodically driven molecular dynamics, essentially leads to an optimally performing optomechanical work cycle for the locomotive beyond any model-based pre-designed version. These findings reveal a great potential of laser optimally controlled nanowork cycles in the emerging field of nanomachinery.
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Affiliation(s)
- Z S Wang
- Institute of Modern Physics, Fudan University, Shanghai 200433, People's Republic of China
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84
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van den Brom AJ, Rakitzis TP, Janssen MHM. State-to-state photodissociation of carbonyl sulfide (ν2=0,1∣JlM). II. The effect of initial bending on coherence of S(D21) polarization. J Chem Phys 2005; 123:164313. [PMID: 16268703 DOI: 10.1063/1.2076647] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Photodissociation studies using ion imaging are reported, measuring the coherence of the polarization of the S((1)D(2)) fragment from the photolysis of single-quantum state-selected carbonyl sulfide (OCS) at 223 and 230 nm. A hexapole state-selector focuses a molecular beam of OCS parent molecules in the ground state (nu2=0mid R:JM=10) or in the first excited bending state (nu2=1mid R:JlM=111). At 230 nm photolysis the Im[a1 (1)(parallel, perpendicular)] moment for the fast S(1D2) channel increases by about 50% when the initial OCS parent state changes from the vibrationless ground state to the first excited bending state. No dependence on the initial bending state is found for photolysis at 223 nm. We observe separate rings in the slow channel of the velocity distribution of S(1D2) correlating to single CO(J) rotational states. The additional available energy for photolysis at 223 nm is found to be channeled mostly into the CO(J) rotational motion. An improved value for the OC-S bond energy D0=4.292 eV is reported.
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Affiliation(s)
- Alrik J van den Brom
- Laser Center and Department of Chemistry, Vrije Universiteit, de Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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85
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van de Meerakker SYT, Smeets PHM, Vanhaecke N, Jongma RT, Meijer G. Deceleration and electrostatic trapping of OH radicals. PHYSICAL REVIEW LETTERS 2005; 94:023004. [PMID: 15698171 DOI: 10.1103/physrevlett.94.023004] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2004] [Indexed: 05/24/2023]
Abstract
A pulsed beam of ground state OH radicals is slowed down using a Stark decelerator and is subsequently loaded into an electrostatic trap. Characterization of the molecular beam production, deceleration, and trap loading process is performed via laser induced fluorescence detection inside the quadrupole trap. Depending on the details of the trap loading sequence, typically 10(5) OH (X2Pi(3/2),J=3/2) radicals are trapped at a density of around 10(7) cm(-3) and at temperatures in the 50-500 mK range. The 1/e trap lifetime is around 1.0 s.
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86
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van den Brom AJ, Rakitzis TP, Janssen MHM. Photodissociation of laboratory oriented molecules: Revealing molecular frame properties of nonaxial recoil. J Chem Phys 2004; 121:11645-52. [PMID: 15634130 DOI: 10.1063/1.1812756] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We report the photodissociation of laboratory oriented OCS molecules. A molecular beam of OCS molecules is hexapole state-selected and spatially oriented in the electric field of a velocity map imaging lens. The oriented OCS molecules are dissociated at 230 nm with the linear polarization set at 45 degrees to the orientation direction of the OCS molecules. The CO(nu=0,J) photofragments are quantum state-selectively ionized by the same 230 nm pulse and the angular distribution is measured using the velocity map imaging technique. The observed CO(nu=0,J) images are strongly asymmetric and the degree of asymmetry varies with the CO rotational state J. From the observed asymmetry in the laboratory frame we can directly extract the molecular frame angles between the final photofragment recoil velocity and the permanent dipole moment and the transition dipole moment. The data for CO fragments with high rotational excitation reveal that the dissociation dynamics is highly nonaxial, even though conventional wisdom suggests that the nearly limiting beta parameter results from fast axial recoil dynamics. From our data we can extract the relative contribution of parallel and perpendicular transitions at 230 nm excitation.
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Affiliation(s)
- Alrik J van den Brom
- Laser Centre and Department of Chemistry, Vrije Universiteit, de Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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