Energy partitioning and spin–orbit effects in the photodissociation of higher chloroalkanes

Abstract

We investigate the photodissociation dynamics of C–Cl bond in chloroalkanes CH3Cl, n-C3H7Cl, i-C3H7Cl, n-C5H11Cl, combining velocity map imaging (VMI) experiment and direct ab initio dynamical simulations. The Cl fragment kinetic...

On the Wavelength-Dependent Photochemistry of the Atmospheric Molecule CF3COCl

“…Another reason might be the inaccurate rigidity of bonds in the electronic structure method, causing a lower effective mass of the dissociating fragments. Such an effect was previously observed, e.g., for alkyl-halogenides . Nevertheless, increasing the rigidity of the structure did not affect the positions of the peaks (Figure S7).…”

“…Such an effect was previously observed, e.g., for alkyl-halogenides. 25 Nevertheless, increasing the rigidity of the structure did not affect the positions of the peaks (Figure S7). The ECC makes an important contribution, the kinetic energies at the pure FOMO-CASCI level deviate from the experiment significantly, yet the timescale remains the same (123 ± 71 fs).…”

“…For the excitation wavelengths 235, 254, and 280 nm, the Cl fragments (meaning both 2 P 3/2 and 2 P 1/2 spin–orbit states) are observed and their KEDs exhibit a single peak with a weak parallel character. The fragment kinetic energy (0.4–0.5 eV at KED maximum) does not correspond to a direct two-body dissociation, which could be approximated by a hard sphere model . Such a model would yield Cl fragment kinetic energies of 1.48, 1.19, and 0.86 eV, respectively, for the above wavelengths [assuming D 0 (C–Cl) = 3.26 eV].…”

“…The experimental procedures were similar to the ones described recently for the photodissociation of methyl chloride 24 and higher chloroalkanes. 25 The sample vapor of CF 3 COCl (abcr GmbH) was premixed in a stainless-steel gas container with helium buffer gas into 1% mixture (1.3 bar) and connected through inlet line to the pulsed nozzle (General Valve) in the source chamber (background vacuum 1 × 10 −7 mbar). The nozzle opens at a repetition rate of 10 Hz, and the supersonic expansion is skimmed to the next chamber to generate a molecular beam.…”

“…The fragment kinetic energy (0.4−0.5 eV at KED maximum) does not correspond to a direct two-body dissociation, which could be approximated by a hard sphere model. 25 Such a model would yield Cl fragment kinetic energies of 1.48, 1.19, and 0.86 eV, respectively, for the above wavelengths [assuming D 0 (C−Cl) = 3.26 eV]. Thus, a relatively large part of the excitation energy is dissipated into the internal excitation of the CF 3 CO fragment (1.36, 1.02, and 0.61 eV, respectively, corresponding to the position of the KED maximum).…”