Resonance Raman spectra were obtained for nitrobenzene in cyclohexane solution with excitation wavelengths in resonance with the charge-transfer (CT) band absorption spectrum. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mainly along the nominal NO2 symmetric stretch mode (v11), the nominal benzene ring stretch mode (v7), accompanied by a moderate degree of motion along the nominal ONO symmetry bend/benzene ring stretch mode (v23), the nominal C-N stretch/benzene ring breathing mode (

Resonance Raman spectra were obtained for cyclopropyl iodide in cyclohexane solution with excitation wavelengths in resonance with the A-band absorption spectrum. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mainly along the nominal C-I stretch and nominal C-C-I deformation normal modes accompanied by moderate motion along the nominal cyclopropyl ring breathing and ring deformation normal modes. A preliminary resonance Raman intensity analysis was done, and the results for cyclopropyl iodide were compared to previously reported results for several cyclic and noncyclic alkyl iodides.

We have obtained A-band resonance Raman spectra of dibromomethane in the gas and solution phase and nanosecond time-resolved resonance Raman spectra of dibromomethane photoproducts. The A-band resonance Raman spectra suggest the short-time dynamics are similar to other dihalomethanes that are known to have direct photodissociation reactions in the gas phase. Several power dependent A-band resonance Raman bands were tentatively assigned to the C-Br stretch overtone progression of the CH2Br radical which has a strong absorption band that is coincident with the A-band resonance Raman excitation wavelength. Two-color nanosecond time-resolved resonance Raman spectra (266.0nm pump/341.5nm probe) were obtained and comparison of the vibrational frequencies to the results for density functional theory calculations indicate that the iso-CH2Br-Br species is mainly responsible for the transient photoproduct absorption band 360nm. Our preliminary results for A-band photoexcitation of dibromomethane in conjunction with previously reported diiodomethane results suggest that solvation effects (probably via recombination of the CH2Br and Br fragments within a solvent cage) lead to noticeable production of the isodibromomethane photoisomerization photoproduct observed in the nanosecond time-resolved resonance Raman spectra.

We report transient resonance Raman experiments that identify isodiiodomethane as the photoproduct responsible for the 385 nm absorption band observed following ultraviolet excitation of diiodomethane in liquid solutions. Comparison with previously reported gas-phase experiments and solution-phase resonance Raman and femtosecond transient absorption results suggest that solvation leads to appreciable production of the isodiiodomethane (H2C-I-I) photoproduct via the interaction of the initially formed CH2I and I fragments with the solvent cage. The isodiiodomethane photoproduct is likely the species or an intermediate to the species that reacts with alkenes in cyclopropanation reactions that use ultraviolet excitation of diiodomethane in liquids.

We have done ab initio calculations to find the equilibrium geometries, rotational/inversion barriers, and harmonic vibrational frequencies of several haloethyl radicals (XCH2CH2 and XCHCH3 where X=F, Cl, Br). One equilibrium and two transition conformations for XCH2CH2 (X=Cl, Br) and XCHCH3 (X=F, Cl, Br) were found on the calculated B3LYP/6-311++G(3df,3pd) potential energy surface. We discuss the effects of the halo substituents on the haloethyl radicals investigated. The C-X bonds of the equilibrium