Kinetic study of electronically excited antimony atoms, Sb(5 2D 3/2,5/2), by time-resolved attenuation of atomic resonance radiation

Abstract

A method is described for the direct kinetic study of electronically excited antimony atoms, Sb(5 2D 3 2 ) and Sb(5 2D 5 2 ), respectively 1.055 and 1.222 eV above the(5 4S 3/2) ground state. These optically metastable atoms were generated by the pulsed irradiation of SbMe 3 and monitored photo-electrically by time-resolved absorption spectroscopy of resonance transitions at λ = 259.81 nm [6 s( 2P 1/2 ← 5 p 3( 2D 3/2)] and λ = 252.85 nm [6 s( 2P 3/2) ← 5 p 3( 2D 5/2)]. These two spin orbit levels, in general, showed different kinetic decays and were clearly not in a Boltzmann equilibrium throughout the rate measurements. Absolute quenching constants for the collision partners He, H 2, O 2, CO, CO 2 and SbMe 3 are reported and compared with the analogous data for the 2D J states of atomic nitrogen, phosphorus and arsenic. Unlike the data for these lighter atoms, which were considered hitherto in terms of symmetry arguments involving the weak spin orbit coupling approximation, the present data are discussed using (J, ω) coupling which is seen to be a more suitable vehicle for interpreting the collisional behaviour of heavy metal atoms in the gas phase.