Kinetic studies of ground state atoms, Sb(54S), by time-resolved resonance fluorescence

Abstract

Ground state antimony atoms, Sb[5p³(⁴S)], have been studied by time-resolved resonance fluorescence at λ= 231.1 nm (6⁴P_½→ 5⁴S) in the “single-shot” mode. The antimony atoms were generated by pulsed irradiation of SbMe₃ using a “magnetically-pinched”, Garton light source with a high spectral output in the vacuum ultraviolet. Optical excitation of the resulting Sb(5⁴S) was effected by means of a sealed microwave-powered atomic emission source, and the resonance fluorescence was monitored photoelectrically with a photomultiplier tube gated with a “pre-trigger” system. Kinetic studies of Sb(5⁴S) in the presence of NO and of O₂ are described and the resulting rate constants are compared with analogous data derived previously using time-resolved resonance absorption at the same wavelength, and discussed in terms of departures from the standard Beer–Lambert law for light absorption. Radiation trapping calculations are also described which involve summation of the Voigt profiles over all the individual nuclear hyperfine components that contribute to the λ= 231.1 nm transition. Solutions of the diffusion equation for radiation with different boundary conditions are employed in the calculations of the relationship between fluorescence intensity and particle density. The results are compared with the experimental fluorescence intensity calibration for this system.