Some features in 4-level generation in LIPLs

TL;DR

This paper investigates the mechanisms of population inversion in Laser-Induced Plasma Lasers (LIPLs), highlighting the role of forbidden transitions, spin-orbit coupling, and electron-atom collisions, supported by TDDFT calculations.

Contribution

It reveals that collisionally assisted transitions can be partly forbidden and that spin-orbit coupling enhances oscillator strength, providing new insights into LIPL energy level dynamics.

Findings

Forbidden transitions can be partially allowed by spin-orbit coupling.

Electron-atom collisions significantly increase atomic energy levels.

Oscillator strengths and transition rates are estimated using TDDFT.

Abstract

This paper shows that in Laser-Induced Plasma Lasers (LIPL), the collisionally assisted transitions that lead to the inversion population on an upper-generation level E_up may be partly forbidden. The spin-orbit coupling may increase the oscillator strength of such transitions. It also demonstrates that collisions between electrons and excited atoms can strongly increase the atoms' energy, creating a population inversion at the E_up level, which may lie about 1 eV above the pumped level E_pump. Examples of oscillator strengths and collisional transition rate estimates are provided using linear-response time-dependent density functional theory (TDDFT) in the Casida formalism.