Alkali-metal negative ions. II. Laser photoelectron spectrometry

Abstract

Photodetachment of alkali-metal negative ions by an Ar-ion laser (4880 Å) has been studied in a crossed-beam geometry. Energy analysis of the photodetached electrons yields the following electron affinities: EA(Li)=(0.620±0.007) eV, EA(Na)=(0.548±0.004) eV, EA(Rb)=(0.486±0.003) eV, and EA(Cs)=(0.470±0.003) eV. These values are obtained relative to an independent measurement of the potassium electron affinity: EA(K)=(0.5012±0.0005). In addition, the angular distribution anisotropy parameter $\beta$ has been measured at 4880 Å for photodetachment processes leaving the neutral in its ground state and in its first excited state. Relative photodetachment cross sections for these two processes are presented for K, Rb, and Cs.