Optimal conditions for generation of three-color metal-vapor ion lasers with a hollow cathode

The dominant pumping mechanism of the 441.6 nm Cd II line in a three-colour hollow-cathode discharge laser

“…The maximum value is at the point where helium and cadmium pressures reach 20 and 0.1 Torr, respectively. This result is in good agreement with our data obtained in experiments with the 441.6 nm laser line in a HCD (Vainer et al 1983, Kalinchenko et al 1989.…”

“…Therefore, to determine the pumping rate of the wher W H e * is the rate of excitation of He, ν H e * is the frequency of elimination of excited helium atoms from the active volume due to all the various processes except the Penning ionization (the most important are diffusion and stepwise ionization). When the density of cadmium atoms increases to 10 15 cm −3 , or higher, the second term in the denominator of ( 14) becomes essentially larger than the first one (Kalinchenko et al 1989). This is possible since radiative resonance transitions to the ground state of the He atom (the shunting Penning process) are 'closed' (Ivanov et al 1972) and both upper excited states and metastable ones take part in the Penning process.…”

Processes in hollow cathode discharge excited by steady-state and pulse currents

“…where v. is the frequency of elastic collisions of electrons with surrounding gas particles [10], f, and Ii are EDF for different intervals of the electron energy namely, f1 describes a highvelocity electrons when they move as a beam, f, is EDF when electrons move as diffusion cloud, e'the threshold energy ofinelastic collisions. The solutions of equations (2) and (3) are given in Appendix.…”

“…The cross sections of metal atom excitation is ten-times more then one of ionization [10]. Meanwhile the time of EDF forming for high-speed electrons is near 1O s. Therefore the regime of excitation by microsecond's pulses is quasi-state for this EDF, and one can solve the stationary equations.…”

“…Therefore, the focusing close to the axis dominates. More over helium ions immediately transfer their charge to metal atoms, and excited helium atoms immediately give the energy to ionise cadmium by Penning collisions [10]). hi) When the helium pressure grows, the number of electrons with energy becomes high enough to produce ionization and excitation of cadmium atoms decreases in the region near the cathode axis.…”