Photoabsorption spectra of the heavy alkali-metal negative ions

The combined use of an eigenchannel R-matrix calculation in jj coupling, and of a generalized quantum-defect treatment of electron escape in a polarization potential, accounts quantitatively for high-resolution photodetachement spectra of Cs^- and Rb^-. The calculation further predicts the existence of three odd-parity 6s6p ³P^∘{} bound states in Cs^- (with J=0,1,2) in addition to the well-known 6s² ground state, confirming earlier evidence derived from studies by Fabrikant [Opt. Spektrosk. 53, 223 (1982); Eng. trans., Opt. Spectrosc. (USSR) 53, 131 (1982)], and by Fischer and Chen [J. Mol. Struc. 199, 61 (1989)] performed in LS coupling. The radiative lifetime of the J=1 excited bound state is predicted to be 0.013 sec, whereas the J=0,2 fine-structure components appear to be unusually long-lived. Photodetachment spectra predicted for Fr^- exhibit resonances near the first excited ²P thresholds of Fr, analogous to those familiar in Rb^- and Cs^-.