Laser-induced fluorescence studies of excited Sr reactions. III. Sr(3P1)+CHF=CH2, CF2=CH2, CHF=CHF, and C6H5F

Abstract

Laser-induced fluorescence spectra reveal the internal energy distributions of SrF(X 2 ⌺) formed in the reactions of electronically excited Sr( 3 P 1 ) with various unsaturated fluorohydrocarbons, i.e., CHFvCH 2 , CF 2 vCH 2 , CHFvCHF, and C 6 H 5 F. The internal energy distribution of the ground state diatomic product typically shows less vibrational excitation, without inversion, and somewhat lower rotational excitation than the reactions of Sr( 3 P 1 ) with HF and saturated hydrocarbons. The different behavior of the two groups of reactants is rationalized by a simple MO picture, assuming that an electron from Sr is transferred to a * orbital in HF and the saturated fluorohydrocarbons and to a * orbital in the unsaturated fluorohydrocarbons with a subsequent transfer to a * orbital of the C-F bond. The latter transfer constitutes an extension of the reaction path, leading to less vibrational excitation. This would explain why the energy disposal in the reaction with C 6 H 5 F behaves similar to that in the reactions with the fluoroethenes. Even if the shape of the vibrational distribution of the SrF product is the same for all unsaturated fluorohydrocarbons studied, the degree of vibrational excitation varies strongly. This even holds when comparing cis-and trans-CHFϭCHF, where the distributions can be characterized by distinct surprisal parameters.

Chemical and Electronic Branching Ratios in the Chemiluminescent Reactions of Hyperthermal Ca(3P) Atoms with CF2Cl2 and CF2CCl2

“…In this work, we found a strong dependence of the chemical branching ratio CaCl/CaF on the specific target molecule. The differences observed for both reaction are rationalized in terms of the harpoon model and the characteristics of the molecular orbital (MO) of the target molecule in which the electron enters, as previously suggested by different authors. − …”

Quasi-classical trajectory study of the reaction dynamics of Ca(1S0,3P) atoms with CHCl3

“…In the past several decades, the detailed reaction dynamics between alkaline earth metal atoms and halogenated methanes has been attracting much extensive attention both theoretically and experimentally [1][2][3][4][5][6][7][8][9]. Laser induced fluorescence (LIF) is the most popular method to study alkaline earth monohalides, and a pulsed laser are also used in most cases [1][2][3][4][5][6][7][8][9][10].…”

“…Specific reactions have been investigated experimentally under single collision conditions for the following reactions, such as Sr + XF (X is alkyl) [1][2][3][4][5][6][7][11][12][13][14][15], Ba + XI (X is alkyl) [10,16,17], Ca/Ba + CH 3 X (X = Br, I) [7,[16][17][18][19], Ba + HX [20], etc. The reaction Ca + CH 3 X (X = Br, I) was investigated by Keijzer et al with continuous-wave LIF spectra [6,7].…”

“…Laser induced fluorescence (LIF) is the most popular method to study alkaline earth monohalides, and a pulsed laser are also used in most cases [1][2][3][4][5][6][7][8][9][10].…”

“…The variation of the disposal into vibrational energy of the formed diatom among the various systems was attributed to a variation of the harpooning radius and its magnitude relative to the interatomic distance of the diatomic product [6,7]. Using Laser-induced chemiluminescence in a beam-gas apparatus, Yang et al [21] have carried out total collision cross-sections and chemiluminescent cross-sections for the Ca( 1 P) + CH 3 Cl, CH 2 Cl 2 , CHCl 3 , and CCl 4 . The reaction cross-section excitation function for the crossed beam reaction was reported as a function of collision energy for reactions of CH 3 I, CD 3 I and CH 3 Br over the range 0.1-1.0 eV by Mackay and co-workers [5] who used a crossed molecular beam apparatus.…”