FROM MONOMERS TO CLUSTERS - PHOTODISSOCIATION OF TERT-BUTYL NITRITE (CH3)(3)CONO AND HOMOGENEOUS [(CH3)(3)CONO](N) CLUSTERS

Homogeneous and neutral clusters of tert-butyl nitrite [(CH3)(3)CONO]( n), with (n) roughly 20, were produced by adiabatic jet expansion and photolyzed via the localized S-1(n pi()) <-- S-0 transition to R + NO ((2) Pi) at lambda(d) approximate to 360-400 nm. Using photofragment yield spectroscopy (PHOFRY), we determined the relative partial absorp tion cross sections leading to NO (nu'' = 0, 1, 2) products from the m onomer and the clusters which allowed us to selectively investigate fr om a monomer/ cluster mixture the cluster formation and the cluster ph otodissociation. The latter was further characterized by the rotationa l state distributions of the four sublevels of NO ((2) Pi(+/-1/2) and (2) Pi(+/-3/2)) and the rotational alignment A(0)(2)). Essentially two types of NO fragments emerged from the photoexcited clusters: one hav ing relaxed J state distributions and no alignment A(0)((2)), the othe r hot (non-Boltzmann) distributions and a strong alignment as well as a preference for the Lambda-state A''. The relaxed NO fragments are pr oposed to arise from nitrite molecules ''solvated'' in the cluster and the hot NO fragments from nitrite molecules with a free chromophore l ocated on the surface of the cluster. The vibrational state population of NO appears no to be significantly influenced by cluster formation.