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Shin SK, Dagdigian PJ. Dynamics of the 193nm photodissociation of dichlorocarbene. J Chem Phys 2006; 125:133317. [PMID: 17029470 DOI: 10.1063/1.2212416] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The dynamics of the 193 nm photodissociation of the CCl2 molecule have been investigated in a molecular beam experiment. The CCl2 parent molecule was generated in a molecular beam by pyrolysis of CHCl3, and both CCl2 and the CCl photofragment were detected by laser fluorescence excitation. The 193 nm attenuation cross section was estimated from the reduction of the CCl2 signal as a function of the photolysis laser fluence. The internal state distribution of the CCl photofragment was derived from analysis of laser fluorescence excitation spectra in the A 2Delta-X 2Pi band system. Most of the energy available to the CCl(X 2Pi)+Cl fragments appears as translational energy. The CCl fragment rotational energy is much less than predicted in an impulsive model. The excited electronic state appears to dissociate indirectly, through coupling with a repulsive state arising from the ground-state CCl(X 2Pi)+Cl asymptote. The identity of the initially excited electronic state is discussed on the basis of what is known about the CCl2 electronic states.
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77
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Zolot AM, Harper WW, Perkins BG, Dagdigian PJ, Nesbitt DJ. Quantum-state resolved reaction dynamics at the gas-liquid interface: Direct absorption detection of HF(v,J) product from F(P2)+Squalane. J Chem Phys 2006; 125:21101. [PMID: 16848566 DOI: 10.1063/1.2217016] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Exothermic reactive scattering of F atoms at the gas-liquid interface of a liquid hydrocarbon (squalane) surface has been studied under single collision conditions by shot noise limited high-resolution infrared absorption on the nascent HF(v,J) product. The nascent HF(v,J) vibrational distributions are inverted, indicating insufficient time for complete vibrational energy transfer into the surface liquid. The HF(v=2,J) rotational distributions are well fit with a two temperature Boltzmann analysis, with a near room temperature component (T(TD) approximately equal to 290 K) and a second much hotter scattering component (T(HDS) approximately equal to 1040 K). These data provide quantum state level support for microscopic branching in the atom abstraction dynamics corresponding to escape of nascent HF from the liquid surface on time scales both slow and fast with respect to rotational relaxation.
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78
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Teslja A, Dagdigian PJ, Banck M, Eisfeld W. Experimental and Theoretical Study of the Electronic Spectrum of the Methylene Amidogen Radical (H2CN): Verification of the 2A1 ← 2B2 Assignment. J Phys Chem A 2006; 110:7826-34. [PMID: 16789769 DOI: 10.1021/jp061578j] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A collaborative experimental and theoretical study of the electronic spectrum and excited-state photochemistry of H(2)CN has been carried out. The absorption spectrum, in the range of 287-278 nm, was measured through cavity ring-down spectroscopy. The radical was prepared by 193 nm photolysis of monomeric formaldoxime vapor. Two diffuse features were observed in the 34800-35800 cm(-1) spectral range, along with the A-X (1,0) band of the OH cofragment. The broad features were assigned through high-level ab initio calculations as vibronic transitions to the ground and 2b(1) (umbrella mode) levels of the second excited B (2)A(1) state from the ground X (2)B(2) state of H(2)CN. Rotational constants for the lower and upper levels of these transitions were computed from the expectation values of the moments of inertia tensor, using the appropriate vibrational wave functions. Experimental and simulated rotational profiles of these bands agree extremely well with each other for an assumed type-B electric dipole-allowed (2)A(1) <-- (2)B(2) transition appropriate to this transition. The former assignment to the dipole-forbidden (2)B(1) <-- (2)B(2) transition can be ruled out by these results. A theoretical investigation of the dissociation pathways for electronically excited H(2)CN is also presented. The upper states of the observed bands cannot dissociate directly but rather decay through internal conversion and subsequent dissociation to H + HCN fragments; higher b(1) levels are above the excited-state dissociation limit.
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79
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Khachatrian A, Dagdigian PJ. Effect of Vibrational Excitation on the Collisional Removal of Free Radicals by Atoms: OH(v=1) + N. J Phys Chem A 2006; 110:3388-92. [PMID: 16526617 DOI: 10.1021/jp0561017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The collisional removal of vibrationally excited OH(upsilon=1) by N(4S) atoms is investigated. The OH radical was prepared by 193 nm photolysis of H2O2, and N(4S) atoms were generated by a microwave discharge in N2 diluted in argon. The concentrations of OH(upsilon=0 and 1) were monitored by laser-induced fluorescence as a function of the time after the photolysis laser pulse. The N(4S) concentration was determined from the OH(upsilon=0) decay rate, using the known rate constant for the OH(upsilon=0) + N(4S) --> H + NO reaction. From comparison of the OH(upsilon=0 and 1) decay rates, the ratio of the rate constant k(upsilon=1)(OH-N) for removal of OH(upsilon=1) in collisions with N(4S) and the corresponding OH(upsilon=0) rate constant, k(upsilon=0)(OH-N) was determined to be 1.61 +/- 0.42, yielding k(upsilon=1)(OH-N) = (7.6 +/- 2.1) x 10(-11) cm3 molecule(-1) s(-1), where the quoted uncertainty (95% confidence limits) includes the uncertainty in k(upsilon=0)(OH-N). Thus, the collisional removal of OH(upsilon=1) by N(4S) atoms is found to be faster than for OH(upsilon=0).
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Abstract
The dynamics of the 248 nm photodissociation of the CCl(2) molecule have been investigated in a molecular beam experiment. The CCl(2) parent molecule was generated in a molecular beam by pyrolysis of CHCl(3), and both CCl(2) and the CCl photofragment were detected by laser fluorescence excitation. The 248 nm attenuation cross sections was estimated from the reduction of the CCl(2) signal as a function of the photolysis laser fluence. The internal state distribution of the CCl photofragment was derived from analysis of laser fluorescence excitation spectra in the A (2)Delta- X (2)Pi band system. The CCl(X (2)Pi, nu = 0) rotational state distribution was found to be bimodal, with maximum populations at N approximately 10 and 85, and was dependent upon the source backing pressure, and hence upon the internal state distribution of the CCl(2) precursor. The 248 nm photodissociation dynamics appears to involve two separate channels, namely nearly impulsive rotational energy release and predissociation with little rotational energy imparted to the CCl fragment.
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81
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82
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Khachatrian A, Dagdigian PJ. Determination of the internal state distribution of the SD product from the S(1D)+D2 reaction. J Chem Phys 2005; 122:024303. [PMID: 15638582 DOI: 10.1063/1.1827598] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The S(1D)+D2-->SD+D reaction has been studied through a photolysis-probe experiment in a cell. S(1D) reagent was prepared by 193 nm photolysis of CS2, and the SD(X 2Pi) product was detected by laser fluorescence excitation. The nascent rotational/fine-structure state distribution of the SD(X 2Pi) product was determined. This reaction, previously studied theoretically and in a crossed molecular beam experiment, is known to proceed through formation and decay of a long-lived collision complex involving the deep well in the H2S ground electronic state. The determined SD rotational state distribution in the v=0 vibrational level was found to be approximately statistical, with a small preference for formation of the F1 (Omega=3/2) fine-structure manifold over F2 (Omega=1/2). The branching into the Lambda doublet levels was also investigated, and essentially equal populations of levels of A' and A" symmetry were found. The present results are compared with previous investigations of this reaction and the analogous O(1D)+D2 reaction.
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83
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Teslja A, Dagdigian PJ. Determination of oxygen atom concentrations by cavity ring-down spectroscopy. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2004.11.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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84
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Tao C, Dagdigian PJ, Alexander MH. Experimental and theoretical investigation of the 3s←2p transition in the BNe2 complex. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2004.04.116] [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]
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85
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86
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Tao C, Dagdigian PJ. Spectroscopic investigation of nonbonding interactions of group-14 atoms with rare gases: the SnAr van der Waals complex. J Chem Phys 2004; 120:7512-9. [PMID: 15267664 DOI: 10.1063/1.1665957] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The laser fluorescence excitation spectra of the SnAr van der Waals complex, in the vicinity of the individual fine-structure lines of the Sn 5s25p6s3P0<-- 5s25p2(3)P atomic resonance transition in the spectral region 317-270 nm are reported. Excited-state (v',0) progressions of bands built upon the individual J'<-- J" fine-structure atomic lines were observed. Because the collisional spin-orbit relaxation was slow, transitions were observed out of the lower SnAr states built upon all the J'' atomic asymptotes. The spectra were interpreted through model potential energy curves based on the isoelectronic SiAr system. Lower bounds to the dissociation energies of all lower SnAr states were determined. The binding energies of the group-13, and -14-atom-argon complexes and the effect of the spin-orbit interaction on moderating nonbonding interactions are discussed.
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87
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Babushok VI, DeLucia FC, Dagdigian PJ, Nusca MJ, Miziolek AW. Kinetic modeling of the laser-induced breakdown spectroscopy plume from metallic lead. APPLIED OPTICS 2003; 42:5947-5962. [PMID: 14594051 DOI: 10.1364/ao.42.005947] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report initial results of a study aimed toward developing a computational fluid dynamics (CFD) model to simulate the laser-induced breakdown spectroscopy (LIBS) plume for the purpose of understanding the physical and chemical factors that control the LIBS signature. The kinetic model developed for modeling studies of the LIBS plume from metallic lead includes a set of air reactions and ion chemistry as well as the oxidization, excitation, and ionization of lead atoms. At total of 38 chemical species and 220 reactions are included in the model. Experimental measurements of the spatial and temporal dependence of a number of lead emission lines have been made of the LIBS plume from metallic lead. The mechanism of generation of excited Pb states in the LIBS plume is analyzed through kinetic modeling and sensitivity analysis. Initial CFD model results for the LIBS plume are presented.
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88
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Tao C, Tan X, Dagdigian PJ, Alexander MH. Experimental and theoretical investigation of the AlH b 3Σ−–a 3Π electronic transition. J Chem Phys 2003. [DOI: 10.1063/1.1573191] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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89
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90
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Nizamov B, Dagdigian PJ. Spectroscopic and Kinetic Investigation of Methylene Amidogen by Cavity Ring-Down Spectroscopy. J Phys Chem A 2003. [DOI: 10.1021/jp022197i] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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91
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Tao C, Dagdigian PJ. Laser fluorescence excitation spectroscopy of the GeAr van der Waals complex. J Chem Phys 2003. [DOI: 10.1063/1.1529662] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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92
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93
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Tao C, Teslja A, Dagdigian PJ, Atahan S, Alexander MH. Laser spectroscopic study of the SiAr van der Waals complex. J Chem Phys 2002. [DOI: 10.1063/1.1473814] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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94
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Dagdigian PJ. Quantum theory of vector correlations in vibrationally mediated photodissociation. J Chem Phys 2002. [DOI: 10.1063/1.1468881] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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95
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96
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Campbell ML, Dagdigian PJ. Effect of spin-orbit state on chemical reactivity: study of chemiluminescent and ground-state products from reaction of strontium(3PJ) with several halogen-containing molecules. J Am Chem Soc 2002. [DOI: 10.1021/ja00276a003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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97
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Patel-Misra D, Dagdigian PJ. Dynamics of the imidogen(X3.SIGMA.-) + nitric oxide (X2.PI.) reaction: internal state distribution of the hydroxyl (X2.PI.) product. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100187a011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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98
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Varley DF, Dagdigian PJ. Product State Distributions and Angular Differential Cross Sections from Photoinitiated Reactions of Chlorine Atoms with Small Hydrocarbons. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100024a028] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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99
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Cox JW, Dagdigian PJ. Single-collision chemiluminescence study of the strontium(7S, 3P0) + nitrous oxide and magnesium(3P0) + nitrous oxide reactions. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100216a010] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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100
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Yang X, Dagdigian PJ. Chemiluminescence spectra and cross sections for the reaction of boron(4p 2P) with hydrogen and deuterium. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100119a006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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