Articles you may be interested inEffect of intramolecular charge transfer on the two-photon absorption behavior of multibranched triphenylamine derivations Tunneling in jet-cooled 5-methyltropolone and 5-methyltropolone-OD. Coupling between internal rotation of methyl group and proton transfer Resonance Raman study of solvent dynamics on the spectral broadening and intramolecular charge transfer of a hemicyanine dye in aqueous solutionThe fluorescence excitation spectrum and the single vibronic level dispersed fluorescence spectra in the region of the S 0 S 1 transition were measured for jet-cooled 1-phenylpyrrole. The 0-0 band was observed at 35 493 cm Ϫ1 . Long and low-frequency progressions with somewhat irregular intensity distributions appeared on both spectra, and were assigned to torsional motion. The torsional energy levels in the S 0 and S 1 states were obtained up to 25 and 16 quanta, respectively. The torsional potentials in both states could be determined from the sufficient number of energy levels observed. In the S 0 state the most stable conformation was determined to be a twisted form with a dihedral angle of 38.7°, where the planar barrier height was calculated to be 457 cm Ϫ1 , and the perpendicular to be 748 cm Ϫ1 . On the other hand, it was discovered that 1-phenylpyrrole in the S 1 state also had a twisted form with a somewhat smaller dihedral angle of 19.8°, and that the barrier to planarity was 105 cm Ϫ1 and to perpendicularity, 1526 cm Ϫ1 . These facts indicated that the electronic excitation caused 1-phenylpyrrole to be rigid to twist. 1-Phenylpyrrole and its derivatives have been reported as a group of twisted intramolecular charge-transfer ͑TICT͒ molecules. No indication of TICT appeared on the shape of the S 1 -state torsional potential determined. The relation between torsional potential and TICT is discussed based on the results of this study.

The photodissociations of two metal nitrosyl compounds, Co(CO) 3 NO and Mn(CO) 4 NO, were studied at 450 nm, in the metal-to-nitrosyl charge-transfer region for both compounds. The rotational distributions of free NO in the V′′ ) 0 vibrational state were determined by laser-induced fluorescence excitation. A Surprisal Analysis shows that the NO population distributions display a dynamical bias toward lower rotation in both compounds. The similarity between the NO rotational distributions is surprising, considering that Co(CO) 3 NO was expected to dissociate through a bent transition state and Mn(CO) 4 NO was not. The spin-orbit populations of the NO products ( 2 Π 1/2 and 2 Π 3/2 ) are equally populated in both compounds, indicating that the electronic surfaces that produce these two states are strongly coupled at the transition state. An upper limit of the M-NO bond dissociation energy is estimated at 52 kcal/mol from the rotational assignments.