We report density functional theory calculation results that examine the ultraviolet electronic transitions of CF2I2 and CH2I2. We make preliminary assignments of several transitions to the ultraviolet absorption spectra of CF2I2 and CH2I2. We compare our present results to previous experimental and computational work. We also examine the molecular orbitals involved in the electronic transitions assigned to the absorption spectra.

We have obtained Raman spectra for neat liquid iodocyclopentane and for two types of solid phases. Ab initio calculations were done to help elucidate the Raman band assignments to either the axial or equatorial conformations of iodocyclopentane. The liquid Raman spectrum displays bands for both axial and equatorial conformations of iodocyclopentane while the two solid phases exhibit a strong preference for either the axial conformation for the annealed solid phase or the equatorial conformation for the unannealed solid phase. We discuss the possible utility for using this phase-dependent conformation selection to examine the conformation dependence of solid-state photochemical reactions.

Resonance Raman spectra of 1,2-diiodoethane in cyclohexane solution have been obtained in the A-band absorption. A resonance Raman intensity analysis was done to examine the short-time photodissociation dynamics of 1, 2-diiodoethane. Significant bond length and bond angle changes were found for both C-I bonds and the C-C bond as well as the CCI and HCH bond angles. Comparison of the Franck–Condon region dynamics of 1,2-diiodoethane with diiodomethane suggests that the degree of coupling of the two C-I chromophores depends on both the relative geometry of the C-I bonds and their relative separation.

Resonance Raman spectra of l-chloro-2-iodoethane in cyclohexane solution are presented for three excitation wavelengths. The fundamentals, overtones and combination bands of the nominal CCCI bend (v10), the nominal C I stretch (v9), and the C-C1 stretch (v8) vibrational modes can account for most of the resonance Raman intensity. The resonance Raman spectra and associated short-time photodissociation dynamics of I-chloro-2-iodoethane are compared with iodoethane and this suggests that the chloroethyl radical receives more internal excitation than the ethyl radical from the A-band photodissociation in as much as the initial dynamics determines the internal excitation of the alkyl radical photoproducts.

Conformation selective resonance emission spectra are reported for gas-phase iodoeyclohexane with excitation wavelengths of 199.8 and 204.2 nm. These spectra reveal seven Franck-Condon active vibrational modes for the axial conformation and eleven Franck-Condon vibrations for the equatorial conformation, and indicate that the initial dynamics on the B- and C-states have a complex multidimensional character with contributions from the CCC, CCH and HCI bending motions, torsional motions, and C-I, C-C, and C-H stretching motions for both conformations. The resonance emission spectra are generally consistent with the previously reported assignments of the far ultraviolet absorption spectra.