External electric field effect on fluorescence spectra of pyrene in solution.

Electrophotoluminescence (E-PL) spectra, i.e., plots of the electric-field-induced change in photoluminescence intensity as a function of wavenumber, have been measured for pyrene solution. At high concentrations of pyrene where excimer fluorescence is observed along with the monomer fluorescence emitted from the locally excited state, both excimer fluorescence and monomer fluorescence are enhanced by application of electric fields. The results show that the nonradiative decay process at the excimer emitting state is decelerated by application of electric fields. It is also found that molecular polarizability of pyrene excimer is larger than that of pyrene monomer in the ground state by ~270 ± 90 Å(3), based on the analysis of the Stark shift of the excimer fluorescence.

Reaction dynamics of O((1)D,(3)P) + OCS studied with time-resolved Fourier transform infrared spectroscopy and quantum chemical calculations.

Time-resolved infrared emission of CO(2) and OCS was observed in reactions O((3)P) + OCS and O((1)D) + OCS with a step-scan Fourier transform spectrometer. The CO(2) emission involves Deltanu(3) = -1 transitions from highly vibrationally excited states, whereas emission of OCS is mainly from the transition (0, 0 degrees , 1) --> (0, 0 degrees , 0); the latter derives its energy via near-resonant V-V energy transfer from highly excited CO(2). Rotationally resolved emission lines of CO (v

Distribution of vibrational states of CO2 in the reaction O((1)D) + CO2 from time-resolved fourier transform infrared emission spectra.

A mixture of O(3) and CO(2) was irradiated with light from a KrF laser at 248 nm; time-resolved infrared emission of CO(2) in the region 2000-2400 cm(-1) was observed with a Fourier transform spectrometer. This emission involves one quantum in the asymmetric stretching mode (nu(3)) of CO(2) in highly vibrationally excited states. The band contour agrees satisfactorily with a band shape calculated based on a simplified polyad model of CO(2) and a vibrational distribution estimated through a statistical partitioning of energy of approximately 13,000 cm(-1), approximately 3100 cm(-1) smaller than the available energy, into the vibrational modes of CO(2). From this model, approximately 44% and 5% of the available energy of O((1)D) + CO(2) is converted into the vibrational and rotational energy of product CO(2), respectively, consistent with previous reports of approximately 50% for the translational energy. An extent of rotational excitation of CO(2) much smaller than that expected from statistical calculations indicates a mechanism that causes a small torque to be given to CO(2) when an O atom leaves the complex CO(3) on the triplet exit surface of potential energy, consistent with quantum-chemical calculations.