RESONANCE ROTATIONAL RAMAN SCATTERING AS A PROBE OF SUBPICOSECOND PHOTODISSOCIATION DYNAMICS

Abstract

The pattern of resonance enhanced rotational ($\Delta J_{1} \neq 0$) Raman transitions may be analyzed to reveal subpicosecond excited rovibronic $lifetimes.^{1}$ This novel scattering technique is applied to determine quantum specific photodissociation rates in small molecules. UV Raman excitation at 212.8 nm, 208 nm, 217 nm, 204 nm, 200 nm, and 192 nm is produced by mixing and anti-stokes Raman shifting Nd:YAG frequencies. Excited state lifetimes of 0.15, .096, and .056 picoseconds (+10%) are found for the $V_{2}^{\prime} = 1, 2, 3$ levels of the $A \leftarrow X$ transition in $NH_{3}$ using this resonance rotational Raman scattering technique. The quantum yield for photo-dissociation is unity at these excitation wavelengths. Results for $ND_{3}$ and $NO_{2}$ will also be presented.