Vibrational Energy Transfer in CO2 Lasers

TLDR

Laser‑excited vibrational fluorescence of the CO₂ asymmetric‑stretching level (00°1) has been studied. The study outlines criteria for selecting molecules with vibrational‑energy‑level patterns that can produce laser systems. The authors analyze CO₂ laser kinetics using a three‑level scheme and describe efforts to develop continuous‑wave lasers in SO₂ and HCN. Measured vibration‑to‑vibration energy‑transfer rates from the CO₂ 00°1 level, including near‑resonant exchange with N₂, agree with calculated laser performance, and small additions of H₂, D₂, or He reduce laser output by deactivating the lower laser level.

Abstract

Laser-excited vibrational fluorescence measurements have been made on the asymmetric-stretching vibrational level (00°1) of CO2. Vibration→vibration energy-transfer rates from this level due to collisions with CO2 and with a number of other collision partners are presented. The rate of near-resonant exchange of vibrational energy between CO2 and N2 (ΔE=18 cm−1) has been measured. The kinetics of the CO2 laser system are analyzed in terms of a three-level scheme. Observed laser performance is compared with that calculated by use of collisional and radiative coupling rates observed in nonionized gases and of electron activation and deactivation rates estimated from CO2 discharge systems. In accordance with the scheme presented, the relative effectiveness of small amounts of added H2, D2, and He on laser output parallels their effectiveness in deactivating the lower laser level. The criteria for selecting molecules with vibrational-energy-level patterns likely to produce laser systems are outlined. Attempts to produce new continuous-wave lasers in SO2 and HCN are described.