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

Abstract

The three most probable processes for pumping of the upper lasing level of the 441.6 nm Cd II line under hollow-cathode discharge conditions, namely Penning ionization, 'direct' and 'stepwise' electron excitation, have been analysed. Atomic ionization and excitation cross sections and the electron distribution function in the energy interval up to 300 eV have been calculated. Radial dependencies of pumping rates of laser transition for a cylindrical cathode cavity and an integral pumping rate have been determined versus the cadmium vapour and helium pressures. It has been shown that the contributions of Penning ionization and direct and stepwise excitations to the pumping rate are strongly dependent on the pressures of discharge components. Contributions of these processes are found to reach up to about 70, 30 and less than 1%, respectively, under optimal conditions for the laser discharge. The comparison of calculated radial pumping rate distributions with experimental data confirmed that the Penning ionization plays the dominant role.

Monte Carlo simulation of cascade relaxation processes after 1s-photoionization of boron in the gas phase

“…Electron-impact excitation and ionization cross sections are calculated in the first Born approximation using the PF wavefunctions. The explicit formulae are given in [15]. The excitation/ionization channels included in the calculation, and their relative contributions to the partial electron-impact cross sections are listed in table 1.…”

About creation of population inversion in mixture of inert noble gas and metal vapor

“…Einstein coefficients A ik for single electron spectra of M + * in the equation (6) and used for the calculations of the constants (7,8) of exciting and de exciting collisional transitions were found in Coulomb approximation. This approximation holds good for the spectrum of metal ions of II nd and III rd groups of the Periodic System.…”

“…Features of excitation by CT and PI in NG HCD and its advantages before excitation in PC explicitly are described by us in [4,8,9]. Their essence consists in the following.…”

“…These constants are determined as [6,9] (7) (8) Here, f ki is the oscillator strength of the transition, T e is the temperature of thermal slow electrons (expressed in eV), T g is the gas temperature (eV), Δε ik is the difference of energy of levels (eV). The cross section Q for collision M + *-M is equal to Q ≈ 3 × 10 -17 cm 2 , and for M + *-He, M + *-Ne, M + *-Ar, M + *-Kr it is equal 3 × 10 -21 , 3.7 × 10 -21 , 10 -20 and 2 × 10 -20 cm 2 respectively [9].…”

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

“…For Penning-process and charge transfer it is supposed that all the helium ions and excited atoms immediately transfer their energy to the metal atoms and do not have enough time to be eliminated from the active region in any other way [1 1]. 12 12 …”