Collisional energy transfer between excited-state strontium and noble-gas atoms

Inert-gas-induced collisional transfer between the first four excited states of Sr has been measured by determining excited-state densities following pulsed laser excitation of the 5 ¹P state. We observe 5 ¹P collisional transfer exclusively to the 4 ³D state, with ({~}800 K) rate coefficients ranging from 0.24 to 2.0×{}10^-11 cm³ s^-1 for the various gases. We also measure 4 ¹{D}₂$ transfer primarily to the 4 $³D state, with rate coefficients of 0.65 to 6.8×{10}^{{{-}}11}$ ${cm}³$ ${s}^{{{-}}1}$. The 4 $³D state radiative lifetime is observed to be 2.9±0.2 μs, collisional mixing between the 4³Dⱼ fine-structure levels is essentially gas kinetic (k{~}5×{}10^-10 cm³ s^-1), and k10^-13 cm³ s^-1 for 4 ³D{→}5 ³P collisional transfer.