Photodissociation Dynamics of S4N4 at 222 and 248 nm
FRANK J SEILER RESEARCH LAB UNITED STATES AIR FORCE ACADEMY CO
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Emission from several electronically excited states of NS is observed when the energetic molecule S4N4 is photolyzed with radiation from an excimer laser. Photolysis at 248 nm generates fluorescence from the B2 Pi sub 12,32, H2 Pi sub 12, G2 Sigma-, and I2 Sigma states of NS. NSB2 Pi sub 12,32 and NSC2 Sigma fluorescence is observed when the photolysis wavelength is changed to 222 nm. The NSH and NSC spectra are postulated to arise from a resonant, interaction between the KrF and KrCl excimer photons, respectively, and vibrationally hot ground state NS. LIF excitation scans on the NS X2 Pi sub 12,32 yields B2 Pi sub 12,32 system confirm the production of rotationally and vibrationally excited NSX up to v 4. A mechanism, based on the experimental data i.e., spectral composition, laser fluence studies, excited state time histories, calculated heats of formation, and Gaussian molecular orbital calculations, is proposed to account for the observed emissions. For photolysis at 248 nm it is hypothesized that a two photon absorption promotes the ground singlet state Of S4N4 to an upper repulsive singlet state, which rapidly dissociates tau 30 ns, producing an acyclic S3N3 fragment and vibrationally excited monomeric NSX. The photofragments can interact further with the excimer radiation to produce NSB and NSH, respectively. A similar mechanism is proposed to account for the presence of the NSB and NSC excited states for the 222 nm photolysis.
- Inorganic Chemistry
- Radiation and Nuclear Chemistry
- Atomic and Molecular Physics and Spectroscopy