Photoelectron angular distribution measurements of C- at visible wavelengths

Photoelectron angular distributions for the laser photodetachment process 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 intense 10 keV C- beam was produced in a caesium sputter-type ion source and mass-selected with a 90 degrees bending magnet. The mass-selected ion beam was subsequently crossed at 90 degrees with a linearly polarized, continuous photon beam. Angular distributions were obtained by measuring 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 photon beam. The photoelectron angular distributions were used to determine asymmetry parameters. The present measurements are in excellent agreement with those of Hall and Siegel at 488.0 and 514.5 nm (1968 J. Chem. Phys. 48 943), and good agreement with a calculation by Cooper and Zare (1968 J. Chem. Phys. 48 942). The photodetachment asymmetry parameters for C- are compared with a recent;measurement of the photodetachment asymmetry parameters for Si-.