Productions of I, I*, and C2H5 in the A-band photodissociation of ethyl iodide in the wavelength range from 245to283nm by using ion-imaging detection

Abstract

Photodissociation dynamics of ethyl iodide in the A band has been investigated at several wavelengths between 245 and 283 nm using resonance-enhanced multiphoton ionization technique combined with velocity map ion-imaging detection. The ion images of I, I(*), and C(2)H(5) fragments are analyzed to yield corresponding speed and angular distributions. Two photodissociation channels are found: I(5p (2)P(3/2))+C(2)H(5) (hotter internal states) and I(*)(5p (2)P(1/2))+C(2)H(5) (colder). In addition, a competitive ionization dissociation channel, C(2)H(5)I(+)+h nu-->C(2)H(5)+I(+), appears at the wavelengths <266 nm. The I/I(*) branching of the dissociation channels may be obtained directly from the C(2)H(5) (+) images, yielding the quantum yield of I(*) about 0.63-0.76, comparable to the case of CH(3)I. Anisotropy parameters (beta) determined for the I(*) channel remain at 1.9+/-0.1 over the wavelength range studied, indicating that the I(*) production should originate from the (3)Q(0) state. In contrast, the beta(I) values become smaller above 266 nm, comprising two components, direct excitation of (3)Q(1) and nonadiabatic transition between the (3)Q(0) and (1)Q(1) states. The curve crossing probabilities are determined to be 0.24-0.36, increasing with the wavelength. A heavier branched ethyl group does not significantly enhance the I(5p (2)P(3/2)) production from the nonadiabatic contribution, as compared to the case of CH(3)I.

UV photodissociation dynamics of iodobenzene: Effects of fluorination

“…As before, 24 associating the peak at highest TKER (TKER max ) in spectra obtained at long photolysis wavelengths with I * products formed in association with C 6 F x H 5−x radicals in their ground vibrational state (i.e., assuming that all of the available energy is partitioned into product translational energy) allows us to obtain values (strictly upper limits) for the various C-I bond strengths, D 0 (C 6 …”

(1+1) Resonance‐Enhanced Multiphoton Ionization and Photodissociation Study of CS2 via the 1B2 State

“…In an analogous study on photodissociation of C 2 H 5 I at 277.5 nm, the ion image of C 2 H 5 + has been obtained following a similar process of one-photon dissociation and twophoton non-resonant ionization. [20] The resulting C 2 H 5 + image with a weaker intensity slightly differs from the (1 + 1) REMPI results, showing an additional bright image in the central region which is ascribed to background interference. On the other hand, can it be possible for the S + and CS + species to be subject to a process of secondary collision ionization by the electrons generated?…”

“…The apparatus, similar to those reported elsewhere, [19,20] consisted of two vacuum chambers for the molecular beam source and the reaction/detector regions, both of which remained at low pressure, about 10 À7 Torr, by a pair of differential pumps. A < 5 % CS 2 sample was carried by helium gas through a pulsed nozzle (General Valve Co.), operating at 10 Hz, and expanded into the source chamber.…”

Photodissociation of (ICN)2 van der Waals dimer using velocity imaging technique

“…[36][37][38][39] In brief, it is consisted of a molecular beam chamber and a detection chamber. In the source chamber, a supersonic beam of ICN dimer was produced by expanding a mixture of 1% ICN ͑99% purity, ACROS͒ in 1 atm helium through a 10 Hz pulsed nozzle.…”