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Abstract
Chemical kinetics and chemical dynamics are distinct but related topics. They arise again in contemporary physical chemistry often in terms of charge carrier processes in new materials which interconvert light and electrical energy on a distribution of time scales. With this recent rise in the application of concepts in kinetics and dynamics to new problems, there has also arisen confusion about the differences and connections between the two. Here, we briefly review the relationship between kinetics and dynamics in chemical processes, with particular emphasis on the photochemical and photophysical response of a system.
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Alexander AJ, Javier Aoiz F, Brouard M, Short J, Simons JP. State-Resolved Stereodynamics of an Insertion Reaction O(1D2) + H2(v= 0, j) → OH(X2Πi;v′, N′, f′) + H. Isr J Chem 2013. [DOI: 10.1002/ijch.199700037] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Butkovskaya NI, Setser DW. Infrared chemiluminescence from water-forming reactions: Characterization of dynamics and mechanisms. INT REV PHYS CHEM 2010. [DOI: 10.1080/0144235021000033381] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- N. I. Butkovskaya
- a Institute of Chemical Physics , Russian Academy of Sciences , Moscow , 117334 , Russian Federation
| | - D. W. Setser
- b Department of Chemistry , Kansas State University , Manhattan , KS , 66506 , USA
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Zolot AM, Nesbitt DJ. Quantum state resolved scattering dynamics of F+HCl→HF(v,J)+Cl. J Chem Phys 2007; 127:114319. [PMID: 17887849 DOI: 10.1063/1.2770464] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
State-to-state reaction dynamics of the reaction F+HCl-->HF(v,J)+Cl have been studied under single-collision conditions using an intense discharge F atom source in crossed supersonic molecular beams at Ecom=4.3(1.3) kcal/mol. Nascent HF product is monitored by shot-noise limited direct infrared laser absorption, providing quantum state distributions as well as additional information on kinetic energy release from high resolution Dopplerimetry. The vibrational distributions are highly inverted, with 34(4)%, 44(2)%, and 8(1)% of the total population in vHF=1, 2, and 3, respectively, consistent with predominant energy release into the newly formed bond. However, there is a small [14(1)%] but significant formation channel into the vHF=0 ground state, which is directly detectable for the first time via direct absorption methods. Of particular dynamical interest, both the HF(v=2,J) and HF(v=1,J) populations exhibit strongly bimodal J distributions. These results differ significantly from previous flow and arrested-relaxation studies and may signal the presence of microscopic branching in the reaction dynamics.
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Affiliation(s)
- A M Zolot
- JILA, National Institute of Standards and Technology and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA
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Zhao LW, Kan W, Yu HT, Fu HG, Sun JZ. Theoretical Study on the Reaction Mechanism of Ketene CH2CO with Isocyanate NCO Radical. CHINESE J CHEM 2007. [DOI: 10.1002/cjoc.200790206] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Olkhov RV, Smith IWM. Rate coefficients for reaction and for rotational energy transfer in collisions between CN in selected rotational levels (XΣ+2, v=2, N=0, 1, 6, 10, 15, and 20) and C2H2. J Chem Phys 2007; 126:134314. [PMID: 17430039 DOI: 10.1063/1.2715594] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Rate coefficients (ktot,Ni) are reported (a) for total removal (reactive+inelastic) of CN(X2Sigma+,v=2,Ni) radicals from selected rotational levels (Ni=0, 1, 6, 10, 15, and 20) and (b) for state-to-state rotational energy transfer (ki-->f) between levels Ni and other rotational levels Nf in collisions with C2H2. CN radicals were generated by pulsed laser photolysis of NCNO at 573 nm. A fraction of the radicals was then promoted to a selected rotational level in v=2 using a tunable infrared "pump" laser operating at approximately 2.45 microm, and the subsequent fate of this subset of radicals was monitored using pulsed laser-induced fluorescence (PLIF). Values of ktot,Ni were determined by observing the decay of the PLIF signals as the delay between pump and probe laser pulses was systematically varied. In a second series of experiments, double resonance spectra were recorded at a short delay between the pump and probe laser pulses. Analysis of these spectra yielded state-to-state rate coefficients for rotational energy transfer, ki-->f. The difference between the sum of these rate coefficients, Sigmafki-->f, and the value of ktot,Ni for the same level Ni is attributed to the occurrence of chemical reaction, yielding values of the rotationally selected rate coefficients (kreac,Ni) for reaction of CN from specified rotational levels. These rate coefficients decrease from (7.9+/-2.2)x10(-10) cm3molecule-1 s-1 for Ni=0 to (0.8+/-1.3)x10(-10) cm3 molecule-1 s-1 for Ni=20. The results are briefly discussed in the context of microcanonical transition state theory and the statistical adiabatic channel model.
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Affiliation(s)
- Rouslan V Olkhov
- University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
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Wittig C, Bezel I. Effective Hamiltonian models and unimolecular decomposition. J Phys Chem B 2006; 110:19850-60. [PMID: 17020370 DOI: 10.1021/jp061859r] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Partitioning Hilbert space into two subspaces by using orthogonal projection operators yields compact forms for effective Hamiltonians for each of the subspaces. When one (the Q space) contains molecular bound states and the other (the P space) contains dissociative continua, a simple form for the non-Hermitian Q-space effective Hamiltonian, H(eff), can be obtained, subject to reasonable approximations. Namely, H(eff) = H0 - ivariant Planck's/2pi Gamma/2, where H0 is Hermitian, and the width operator variant Planck's/2pi Gamma accounts for couplings of the Q-space levels to the P-space continua. The P/Q partitioning procedure has been applied in many areas of atomic, molecular, and nuclear physics with widespread success. Inputting into this formalism ideas from random matrix theory in order to model independent open channels yields the random matrix H(eff) model. Despite numerous efforts, this model has failed to model satisfactorily the statistical transition-state theory of unimolecular decomposition (hereafter referred to as TST) in the regime of overlapping resonances, where nearly all such reactions occur. All statistical models of unimolecular decomposition are premised on rapid intramolecular vibrational redistribution (IVR) for a given set of good quantum numbers. The phase space thus accessed results in a threshold reaction rate of 1/h rho, and for K independent open channels, the rate is K/h rho. This reaction rate corresponds to a resonance width of K/2pi rho, and when K increases, the resonances (which are rho(-1) apart) overlap. In this regime, the random matrix H(eff) model fails because it does not introduce independent open channels. To illustrate the source of the problem, an analysis is carried out of a simple model that is obviously and manifestly inconsistent with TST. This model is solved exactly, and it is then put in the form of the random matrix H(eff) model, illustrating the one-to-one correspondence. This reveals the deficiencies of the latter. In manipulating this model into the form H0 - ivariant Planck's/2pi Gamma/2, it becomes clear that the independent open channels in the random matrix H(eff) model are inconsistent with TST. Rather, this model is one of gateway states (i.e., bound states that are coupled to their respective continua as well as to a manifold of zero-order bound states, none of which are coupled directly to the continua). Despite the fact that the effective Hamiltonian method is, by itself, beyond reproach, the random matrix H(eff) model is flawed as a model of unimolecular decomposition in several respects, most notably, bifurcations of the distributions of resonance widths in the regime of overlapping resonances.
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Affiliation(s)
- Curt Wittig
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
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Neumark DM. Probing the transition state with negative ion photodetachment: experiment and theory. Phys Chem Chem Phys 2005; 7:433-42. [DOI: 10.1039/b417886f] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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9
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Abstract
The photochemical [small alpha]-cleavage of acetone is analyzed in view of recent results obtained for the isolated molecule in supersonic jets. The fluorescence decay time of the isolated molecule spans a range of more than six orders of magnitude, from approximately 10(-6) s near the origin of the S(0)-S(1) transition to less than 10(-12) s at about 20 kcal x mol(-1) excess energy. In contrast, the decay time of the excited singlet (S(1), (1)n pi) in the bulk is around 10(-9) s and independent of excitation wavelength. Initial excitation to the (1)npi state is followed by internal conversion (IC) to the ground state and intersystem crossing to the lowest-lying triplet. The rate constants of these processes are comparable to the radiative decay rate constant for excess energy up to 7 kcal x mol(-1) above the origin of the S(0)-S(1) transition. Beyond that energy, the triplet state becomes dissociative and the ISC rate becomes much larger than other processes depleting S(1). The primary reaction on the triplet surface is a barrier-controlled alpha-cleavage to form the triplet radical pair CH(3)(*)+ CH(3)CO(*). Direct reaction from the S(1) is negligible, and the non-quenchable reaction (by triplet quenchers) observed in the bulk gas phase is due to hot triplet molecules that dissociate on the timescale of 10(-12) s or less. The singlet-state decay time measured in the bulk (approximately 1-2 ns) arises from collision-induced processes that populate low-lying levels of S(1). The analysis is aided by detailed state-resolved studies on related molecules (in particular formaldehyde and acetaldehyde) whose photophysics and photochemistry parallel those of acetone.
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Affiliation(s)
- Yehuda Haas
- Department of Physical Chemistry and the Farkas Center for Light-Induced Processes, The Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel
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Reiche F, Abel B, Beck RD, Rizzo TR. Double-resonance overtone photofragment spectroscopy oftrans-HONO. II. State- and time-resolved dissociation and OH-product state distributions. J Chem Phys 2002. [DOI: 10.1063/1.1471236] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Geremia JM, Rabitz H. The Ar–HCl potential energy surface from a global map-facilitated inversion of state-to-state rotationally resolved differential scattering cross sections and rovibrational spectral data. J Chem Phys 2001. [DOI: 10.1063/1.1402997] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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Bar I, Rosenwaks S. Controlling bond cleavage and probing intramolecular dynamics via photodissociation of rovibrationally excited molecules. INT REV PHYS CHEM 2001. [DOI: 10.1080/01442350110076484] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Kosterev AA, Makarov AA, Malinovsky AL, Petrova IY, Ryabov EA, Letokhov VS. Transition Spectra in the Vibrational Quasicontinuum of Polyatomic Molecules: Raman Spectra of Highly Excited UF 6 Molecules. J Phys Chem A 2000. [DOI: 10.1021/jp000928d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A. A. Kosterev
- Institute of Spectroscopy, Russian Academy of Sciences, 142190 Troitsk, Moscow Region, Russia
| | - A. A. Makarov
- Institute of Spectroscopy, Russian Academy of Sciences, 142190 Troitsk, Moscow Region, Russia
| | - A. L. Malinovsky
- Institute of Spectroscopy, Russian Academy of Sciences, 142190 Troitsk, Moscow Region, Russia
| | - I. Yu. Petrova
- Institute of Spectroscopy, Russian Academy of Sciences, 142190 Troitsk, Moscow Region, Russia
| | - E. A. Ryabov
- Institute of Spectroscopy, Russian Academy of Sciences, 142190 Troitsk, Moscow Region, Russia
| | - V. S. Letokhov
- Institute of Spectroscopy, Russian Academy of Sciences, 142190 Troitsk, Moscow Region, Russia
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Lara M, Aguado A, Paniagua M, Roncero O. State-to-state reaction probabilities using bond coordinates: Application to the Li+HF(v, j) collision. J Chem Phys 2000. [DOI: 10.1063/1.481982] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Abstract
▪ Abstract This article reviews recent progress in our understanding of gas-phase neutral reaction dynamics as made possible by improvements in the crossed molecular beam scattering technique for measuring reactive differential cross sections. A selection of crossed-beam studies on systems that play a fundamental role in our basic understanding of reaction phenomena are discussed to illustrate the capabilities of the experimental method. The examples include benchmark atom-diatom abstraction and insertion reactions, and four-atom radical reactions for which state-to-state, state-resolved, or state-averaged differential cross sections have recently been measured. The results are discussed in the light of the latest related theoretical developments regarding the treatment of potential energy surfaces and the dynamics of the systems. Recent results on crossed-beam studies of chemically relevant reactions of carbon, nitrogen, and oxygen atoms are also reviewed, and the latest developments in the technique are noted.
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Affiliation(s)
- P Casavecchia
- Dipartimento di Chimica, Università di Perugia, 06123 Perugia, Italy.
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Drabbels M, Wodtke AM. Collisions and Chemistry of Super-Excited Molecules: Experiments Using the PUMP−DUMP−PROBE Technique. J Phys Chem A 1999. [DOI: 10.1021/jp990972x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Marcel Drabbels
- Department of Chemistry, Swiss Federal Institute of Technology Lausanne, CH-1015 Lausanne EPFL, Switzerland
| | - Alec M. Wodtke
- Department of Chemistry, University of California at Santa Barbara, Santa Barbara California 93106
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Lee SH, Lai LH, Liu K, Chang H. State-specific excitation function for Cl(2P)+H2 (v=0,j): Effects of spin-orbit and rotational states. J Chem Phys 1999. [DOI: 10.1063/1.478735] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Srinivasan J, Allison TC, Schwenke DW, Truhlar DG. Transition State Resonances in the Reaction Cl + H2 → HCl + H. J Phys Chem A 1999. [DOI: 10.1021/jp984549k] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jay Srinivasan
- Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, and NASA Ames Research Center, Mail Stop 230-3, Moffett Field, California 94035-1000
| | - Thomas C. Allison
- Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, and NASA Ames Research Center, Mail Stop 230-3, Moffett Field, California 94035-1000
| | - David W. Schwenke
- Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, and NASA Ames Research Center, Mail Stop 230-3, Moffett Field, California 94035-1000
| | - Donald G. Truhlar
- Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, and NASA Ames Research Center, Mail Stop 230-3, Moffett Field, California 94035-1000
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Terentis AC, Waugh SE, Metha GF, Kable SH. HCO (N,Ka,Kc,J) distributions from near-threshold photolysis of H2CO (J,Ka,Kc). J Chem Phys 1998. [DOI: 10.1063/1.475736] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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de Miranda MP, Clary DC, Castillo JF, Manolopoulos DE. Using quantum rotational polarization moments to describe the stereodynamics of the H+D2(v=0,j=0)→HD(v′,j′)+D reaction. J Chem Phys 1998. [DOI: 10.1063/1.476369] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Wade EA, Mellinger A, Hall MA, Moore CB. How a Transition State Tightens: The Singlet Photodissociation of Ketene as a Test Case. J Phys Chem A 1997. [DOI: 10.1021/jp9707652] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Elisabeth A. Wade
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Axel Mellinger
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Melonie A. Hall
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - C. Bradley Moore
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720-1460
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Dulligan M, Tuchler M, Zhang J, Kolessov A, Wittig C. HCO rotational excitation in the photoinitiated unimolecular decomposition of H2CO. Chem Phys Lett 1997. [DOI: 10.1016/s0009-2614(97)88038-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Brownsword R, Hillenkamp M, Schmiechen P, Volpp HR, Wolfrum J. The dynamics of the OH + HD gas-phase reaction: absolute reaction cross section and H/D atom product branching ratio. Chem Phys Lett 1997. [DOI: 10.1016/s0009-2614(97)00719-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Houston PL. New Laser-Based and Imaging Methods for Studying the Dynamics of Molecular Collisions. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp960131f] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Paul L. Houston
- Department of Chemistry, Cornell University, Ithaca, New York 14853-1301
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Molina MJ, Molina LT, Golden DM. Environmental Chemistry (Gas and Gas−Solid Interactions): The Role of Physical Chemistry. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp960146d] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mario J. Molina
- Department of Earth, Atmospheric and Planetary Sciences and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Luisa T. Molina
- Department of Earth, Atmospheric and Planetary Sciences and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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Crim FF. Bond-Selected Chemistry: Vibrational State Control of Photodissociation and Bimolecular Reaction. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp9604812] [Citation(s) in RCA: 300] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- F. Fleming Crim
- Department of Chemistry, University of WisconsinMadison, Madison, Wisconsin 53706
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