Reasons for a reduction in the efficiency of a pulse-periodic CO₂laser with a non-self-sustained discharge at increased input energies

Abstract

We have measured and calculated the P 3 collision Stokes parameter for electron-impact collisional de-excitation to the ytterbium (. . . 6s6p 3 P 1 ) level from the higher-lying 1 P 1 , 3 D 1,2,3 and 3 S 1 levels for 20 eV residual energy. These processes are the time-reverse of the experimentally measured processes, where an impact energy of 20 eV was used to collisionally excite the 3 P 1 target, prepared by resonant laser pumping. Measurements were performed using a crossed-beam apparatus, where excited-state atomic targets were produced using resonant laser radiation incident on the electron-atom interaction region. Calculations were performed in the relativistic convergent close-coupling , convergent close-coupling and relativistic distorted-wave approximations. The theoretical calculations show that the h electron-impact coherence parameter (EICP) is equal to 1/2, independent of the scattering angle. We use this result to present the L ⊥ EICP for the (. . . 6s7s 3 S 1 )→(. . . 6s6p 3 P 1 ) collision process.