Radiative lifetimes ofsanddstates of potassium

The radiative lifetimes of the $7s-11s$ and $5d-9d$ states of potassium have been measured by means of a time- and wavelength-resolved laser-induced-fluorescence approach. The observed lifetimes (in μsec), measured at a temperature of 355 K, of the $7s-11s$ states are 0.165(12), 0.260(14), 0.441(38), 0.60(13), and 0.91(12). The observed lifetimes (in μsec) of the $5d-9d$ states are 0.61(9), 0.89(6), 1.21(10), 1.59(13), and 2.04(30). The measured $s$-state lifetimes are roughly a factor of 2 shorter than the hydrogenic ones, and the measured $d$-state lifetimes are roughly a factor of 10 longer than the hydrogenic ones. The $d$-state lifetimes are reduced from the 0-K radiative lifetimes by as much as 20% by stimulated emission and absorption induced by blackbody radiation. For both $s$ and $d$ states the calculated and observed values of 355-K lifetimes agree to within 10%.