PHOTOELECTRON ANGULAR-DISTRIBUTION MEASUREMENTS OF C- AT VISIBLE WAVELENGTHS

Photoelectron angular distributions for the laser photodetachment proc ess C-(1s(2)2s(2)2p(3 4)S) + hv --> C(1s(2)2s(2)2p(2 3)P) + e(-) have been measured at six wavelengths in the region 457.9-647.1 nm. An inte nse 10 keV C- beam was produced in a caesium sputter-type ion source a nd mass-selected with a 90 degrees bending magnet. The mass-selected i on beam was subsequently crossed at 90 degrees with a linearly polariz ed, continuous photon beam. Angular distributions were obtained by mea suring the laboratory-frame energy spectra of photodetached electrons as a function of the angle between the velocity vector of the ejected electrons and the polarization direction of the linearly polarized pho ton beam. The photoelectron angular distributions were used to determi ne asymmetry parameters. The present measurements are in excellent agr eement with those of Hall and Siegel at 488.0 and 514.5 nm (1968 J. Ch em. Phys. 48 943), and good agreement with a calculation by Cooper and Zare (1968 J. Chem. Phys. 48 942). The photodetachment asymmetry para meters for C- are compared with a recent;measurement of the photodetac hment asymmetry parameters for Si-.