Jl. Chang et al., A new sub-Doppler fluorescence imaging method in studying laser ablation of B atoms at 248 nm, J PHYS CH B, 105(22), 2001, pp. 5079-5082
A new sub-Doppler fluorescence imaging method has been applied to study the
laser ablation of B atoms at 248 nm with a power density of similar to1.7
x 10(8) W/cm(2). Two-dimensional velocity distributions of the laser ablate
d B(P-2 degrees (1/2,3/2)) atoms are measured. The angular distributions of
the ablated B atoms are velocity-dependent. the higher the speed of the B
atom is, the more centralized the distribution of the forward peaking will
be, indicating that the ablation plume undergoes an unsteady adiabatic expa
nsion. The speed distributions of the B atoms are well fitted to the shifte
d Maxwellian functions and are found to be bimodal, including a fast compon
ent with a temperature of 1.8 x 10(4) K topping out at 5.8 eV and a slow co
mponent of 3.1 x 10(3) K reaching a maximum at 2.8 eV. While a plasma react
ion is responsible for the fast component, the slow one results from photoc
hemical processes.