REACTIONS OF ELECTRONICALLY EXCITED BORON ATOMS - QUENCHING RATE CONSTANTS AND THE RADIATIVE LIFETIME OF THE 4P 2P STATE

Collisional quenching and radiative decay of the 4p 2P level of the boron atom has been studied in a cell experiment, in which B atoms are prepared by 266 nm multiphoton dissociation of BBr3 and the 4p 2P level is prepared by sequential 2-photon absorption through the 3s 2S level. A radiative lifetime of 360 +/- 50 ns is derived for B (4p 2P) by extrapolation of the measured decay rates versus BBr3 partial pressure in several Torr helium buffer gas. Bimolecular quenching rate constants were also determined for a number of atomic and molecular species from the dependence of the B (4p 2P) decay rate on the quencher ps partial pressure. The quenching rate constants for the molecular species were quite large (almost-equal-to (1-2) x 10(-9) molecule-1 cm3 s-1), presumably reflecting the small B(4p 2P) ionization potential and the rapid removal of the excited state by chemical reaction.