High resolution electronic spectroscopy of inorganic molecules seeded into a supersonic free jet

Firth, Steven (1986) High resolution electronic spectroscopy of inorganic molecules seeded into a supersonic free jet. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The laser induced fluorescence spectrum of jet cooled chromyl fluoride in the region 18000 cm^-1 to 18600 cm^-1 is reported, and a rotational analysis of the lowest energy band, at 18373 cm^-1, is presented. The excited state is shown to have B₁ symmetry, and this band is believed to be the origin of a ¹B₁ -¹A₁ electronic transition. The B₁ state is shown to be heavily perturbed, levels with J'>3 are not seen, and are presumably predissociated. There is also an a/b inertial axis interchange in this state relative to the ground state. Transitions to some perturbing levels are also seen in this spectrum. The apparatus used in generating the supersonic expansion is discussed and described in detail, and preliminary experiments attempting to seed high temperature species into such an expansion are also described. Calculations are performed on the variation of the bending vibrational energy levels of a triatomic molecule in a Π electronic state with the Renner parameter, ϵ. By diagonalising the Renner-Teller Hamiltonian at several values of ϵ, a plot of bending vibrational energy against ϵ is made. Such diagrams have been drawn before, but only semi-quantitatively, and show some anomalies. Those diagrams are compared with those obtained in this work, and the differences noted. A previously developed model of the Renner-Teller effect is used to analyse the vibrational structure of part of the Ã~X transition of the C₃ molecule, and this analysis is compared with a previous analysis of the same spectrum using a more complex model of the Renner-Teller effect. Initial calculations on the Renner-Teller effect in the ~X ^2Πg state of BO₂ are described. (D71561/87)