High-resolution photodetachment studies ofP−andTe−

Abstract

The photodetachment spectra of ${\mathrm{P}}^{-}$ and ${\mathrm{Te}}^{-}$ are measured in the wavelength region where excitation of the first excited state of P and the ground state of Te becomes energetically possible. A crossed ion-laser beam apparatus is used to measure relative total cross sections from the production of neutral atoms, while the ${\mathrm{P}}^{-}$→P ground- and excited-state partial cross sections are separately determined by means of kinetic energy analysis of the photoelectrons. The spectra allow determination of the P and Te electron affinities (EA), which are found to be 0.7464(4) and 1.9708(3) eV, respectively. The fine-structure intervals of the negative ions are found to be $\Delta E_{J(2-1)\mathrm{}}\left({\mathrm{P}}^{-}\right)=181\mathrm{}\left(3\right)\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, $\Delta E_{J(2-0)\mathrm{}}\left({\mathrm{P}}^{-}\right)=263\mathrm{}\left(3\right)\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, and $\Delta E_{J(\frac{3}{2}-\frac{1}{2})}\left({\mathrm{Te}}^{-}\right)=5008\mathrm{}\left(5\right)\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$. Comparison is made with previous measurements and values which are predicted from extrapolations. A comparison of the ${\mathrm{P}}^{-}$ multichannel measurements is made with equivalent measurements involving alkali negative ions on the basis of channel coupling. In addition, the relative strengths of the various fine-structure level transitions in ${\mathrm{P}}^{-}$→P are determined; the observed strengths agree much better with the predictions of a geometrical model, than with those made by a statistical-weight argument.