On the UV photodissociation dynamics of hydrogen iodide

Langford, Stephen R.; Regan, Paul M.; Orr‐Ewing, Andrew J.; Ashfold, Michael N. R.

doi:10.1016/s0301-0104(98)00013-5

Cited by 68 publications

(53 citation statements)

References 35 publications

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“…Our recent studies of PhI photolysis hinted at a somewhat different mechanism for forming C3 products, more reminiscent of that invoked in explaining the photofragmentation of HI. 51 Most of the energy available to C3 products formed at long photolysis wavelengths is partitioned into translational energy (see Fig. 4).…”

Section: C3mentioning

confidence: 99%

UV photodissociation dynamics of iodobenzene: Effects of fluorination

Murdock

Crow

Ritchie

et al. 2012

The Journal of Chemical Physics

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The UV photochemistry of various fluorinated iodobenzenes (4-fluoro-, 2,4-difluoro-, 3,5-difluoro-, and perfluoro-iodobenzene) has been investigated at many wavelengths by velocity map imaging, time-resolved near infrared absorption spectroscopy and (spin-orbit resolved) ab initio calculations of the ground and excited state potentials along the C-I stretch coordinate, R(C-I). The textbook description of the near UV photochemistry of CH(3)I, i.e., σ∗←n excitation to the (3)Q(0+) state, followed by direct dissociation (to yield spin-orbit excited iodine atom (I∗) products) or by non-adiabatic coupling via a conical intersection (CI) with the (1)Q(1) potential (to yield ground state iodine (I) atoms) is shown to provide a good zero-order model for aryl iodide photochemistry also. However, the aryl halides also possess occupied π and low-lying π∗ orbitals, and have lower (C(2v) or C(s)) symmetry than CH(3)I. Both of these factors introduce additional subtleties. For example, excitations to and predissociation of ππ∗ excited states provide additional routes to I products, most obviously at long UV wavelengths. nσ∗∕πσ∗ configuration mixing stabilizes the (analogue of the) (3)Q(0+) potential energy surface (PES), to an extent that scales with the degree of fluorination; the corresponding 4A(1) PES in C(6)F(5)I is actually predicted to exhibit a minimum at extended R(C-I). This has the effect of extending the long wavelength threshold for forming I∗ products. The lowered symmetry enables an additional (sloped) CI with the 5A(2) (9A(") in 2,4-difluorobenzene) PES, which provides an extra non-adiabatic route to (fast) ground state I atoms when populating the 4A(1) PES at shorter UV excitation wavelengths.

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Section: C3mentioning

confidence: 99%

UV photodissociation dynamics of iodobenzene: Effects of fluorination

Murdock

Crow

Ritchie

et al. 2012

The Journal of Chemical Physics

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“…The HBr molecule was chosen since its photodissociation has been studied in great detail by the TOF technique in the gas phase [30][31][32] and in various clusters, 8-10, 13, 33-37 and it has also been studied by imaging technique in the gas phase. We investigate HBr photodissociation in large clusters of tens to hundreds rare gas atoms.…”

Section: Introductionmentioning

confidence: 99%

Velocity map imaging of HBr photodissociation in large rare gas clusters

Fedor

Kočišek

Poterya

et al. 2011

The Journal of Chemical Physics

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We have implemented the velocity map imaging technique to study clustering in the pulsed supersonic expansions of hydrogen bromide in helium, argon, and xenon. The expansions are characterized by direct imaging of the beam velocity distributions. We have investigated the cluster generation by means of UV photodissociation and photoionization of HBr molecules. Two distinct features appear in the hydrogen atom photofragment images in the clustering regime: (i) photofragments with near zero kinetic energies and (ii) "hot" photofragments originating from vibrationally excited HBr molecules. The origin of both features is attributed to the fragment caging by the cluster. We discuss the nature of the formed clusters based on the change of the photofragment images with the expansion parameters and on the photoionization mass spectra and conclude that single HBr molecule encompassed with rare gas "snowball" is consistent with the experimental observations.

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“…Electronic mail: Gabriel.Balint-Kurti@bristol.ac.uk function of photolysis wavelength have been carried out as has been done for HCl, 1,2 HBr, 15 and HI. 22,23 This article reports the first theoretical study of the spinorbit branching in the photodissociation of HF. Section II details how the time-dependent wave packet technique was used to determine the total and partial cross-sections, and, subsequently, the F* branching fraction over a large excitation energy region.…”

Section: Introductionmentioning

confidence: 99%