The Position, Shape, and Polarization Dependence of Resonances in the Laser Photoionization Spectrum of Aligned Ca 4s5p 1P1

Two-color spectroscopy using narrow-bandwidth pulsed lasers provides a powerful tool to study the near threshold photoionization spectrum of excited atomic states. By combining the energy and polarization selectivity afforded by pulsed dye lasers, it is possible to probe a number of different continua. Many of these would be unreachable from the ground state because of angular momentum and parity selection rules and also due to the lack of high resolution sources of photons at appropriate energies. Precise positions, shape profiles, and strengths of autoionizing resonances, as well as angular distributions of ejected photoelectrons are necessary for comparison with increasingly sophisticated calculations.