Oriented molecule beams: Focusing and orientation of t‐butyl iodide with analysis by polarized laser photofragmentation

Resonance Raman study of the A-band short-time photodissociation dynamics of 2-iodothiophene

Resonance Raman spectra were obtained for 2-iodothiophene in cyclohexane solution with excitation wavelengths in resonance with the A-band absorption spectrum. These resonance Raman spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mainly along the nominal symmetric C=C stretch of the thienyl ring and accompanied by a moderate amount of motion along the nominal symmetric CSC stretch, the nominal antisymmetric CSC stretch, and the nominal C-I stretch vibrational modes. A preliminary resonance Raman intensity analysis was done for the A-band resonance Raman spectra of 2-iodothiophene. These results were compared to previous results for related iodobenzene and iodoalkane molecules that also contain a C-I chromophore and the similarities and differences in the short-time photodissociation dynamics were discussed.

Spin–orbit ab initio study of alkyl halide dissociation via electronic curve crossing

An ab initio study of the role of electronic curve crossing in the photodissociation dynamics of the alkyl halides is presented. Recent experimental studies show that curve crossing plays a deterministic role in deciding the channel of dissociation. Coupled repulsive potential energy curves of the low-lying n-sigma(*) states are studied including spin-orbit and relativistic effects. Basis set including effect of core correlation is used. Ab initio vertical excitation spectra of CH(3)I and CF(3)I are in agreement with the experimental observation. The curve crossing region is around 2.371 A for CH(3)I and CF(3)I. The potential curves of the repulsive excited states have larger slope for CF(3)I, suggesting a higher velocity and decreased intersystem crossing probability on fluorination. We also report the potential curves and the region of curve crossing for CH(3)Br and CH(3)Cl.