State-resolved rotational energy transfer in open shell collisions: Cl(2P3/2)+HCl

Abstract

Time- and frequency-resolved infrared (IR) laser absorption methods are used to probe hot atom energy transfer in open shell interactions of Cl(2P3/2)+HCl(J) in the single collision regime. The Cl(2P3/2) atoms are prepared by 308 nm laser photolysis of Cl2, and suffer collisions at Erel̄∼3500 cm−1 with a room temperature HCl distribution in a fast flow cell. Selective collisional excitation of final HCl(Jf) states is monitored by transient IR absorption on R(J≥4) branch lines in the HCl(v=1←0) band, while depletion of the initial HCl(Ji) states is monitored by transient bleaching of the room temperature Doppler profiles. Analysis of the J dependent Doppler profiles permits extraction of rotational loss [σloss(Ji)=∑fP(Ji)⋅σf←i] and gain [σgain(Jf)=∑iP(Ji)⋅σf←i] cross sections, as a function of initial and final J states, respectively. Absolute transient concentrations of the HCl(Ji) and HCl(Jf) are measured directly from absorbances via Beer’s Law, and used to extract absolute collisional cross sections. The results are compared with quasiclassical trajectory (QCT) calculations on a hybrid ab initio/LEPS surface of Schatz and Gordon, which prove remarkably successful in reproducing both the J dependent trends and absolute values of the state-resolved gain and loss collision cross sections.

Librational Control of Photochemical Reactions in Small Clusters

“…[23][24][25][26][27][28][29][30] The van der Waals region of the system, corresponding to the Cl‚‚‚HCl cluster, has been mapped in terms of potentials and vibrational/librational eigenstates. 31 It follows from this analysis that the Cl‚‚‚HCl cluster should be more stable than its thoroughly investigated closed-shell Ar‚‚‚HCl analogue, and the possibility of the isolation of the Cl‚‚‚HCl species under supersonic jet conditions has been considered.…”

“…The ClHCl species has been intensively studied both theoretically and experimentally in connection with the symmetric hydrogen exchange reaction Cl + HCl → HCl + Cl and the strongly exothermic Cl 2 + H → HCl + Cl exchange reaction. − The van der Waals region of the system, corresponding to the Cl···HCl cluster, has been mapped in terms of potentials and vibrational/librational eigenstates . It follows from this analysis that the Cl···HCl cluster should be more stable than its thoroughly investigated closed-shell Ar···HCl analogue, and the possibility of the isolation of the Cl···HCl species under supersonic jet conditions has been considered …”

Product State Resolved Study of the Cl + (CH3)3CD Reaction: Comparison of the Dynamics of Abstraction of Primary versus Tertiary Hydrogens

“…This reaction is one of a growing number of examples of photoinitiated reactions and energy-transfer processes for which vector correlations have been derived. [4][5][6][7][8][9][10][11] Yen et al 12,13 have also employed REMPI detection in order to investigate site specificity in the reaction of Cl atoms with selectively deuterated propane and butane isotopomers. In all these experiments, the reaction was initiated by photolysis of a Cl atom precursor.…”

“…angular distribution from analysis of the projection of the HCl product laboratory velocity distribution along the TOFMS axis. This reaction is one of a growing number of examples of photoinitiated reactions and energy-transfer processes for which vector correlations have been derived. − Yen et al. 12, 13 have also employed REMPI detection in order to investigate site specificity in the reaction of Cl atoms with selectively deuterated propane and butane isotopomers.…”

State-resolved, three-dimensional product recoil velocity spectroscopy

“…[5][6][7][8][9][10][11][12][13] Using tunable lasers, the frequency profile of a spectral line can be measured, and mapping of this frequency profile into the velocity domain through the Doppler effect gives a one-dimensional projection of the full three-dimensional velocity distribution of the probed molecules. By exploiting the polarized nature of the laser light and the optical transitions involved, information about vector correlations between the velocity and other characteristics of the probed species can also be obtained.…”