Date of Award

3-23-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Engineering Physics

First Advisor

Glen P. Perram, PhD.

Abstract

Pulsed excitation on the two-photon Cs 62S½ → 72D3/2,5/2 transition results in time-resolved fluorescence at 697 nm and 672 nm. The rates for fine structure mixing between the 72D3/2,5/2 states have been measured for helium and argon rare gas collision partners. The mixing rates are very fast, 1.26 ± 0.05 x 10-9 cm3/(atom sec) for He and 1.52 ± 0.05 x 10-10 cm3 /(atom sec) for Ar, driven by the small energy splitting and large radial distribution for the valence electron. The quenching rates are considerably slower, 6.84 ± 0.09 x 10-11 cm3 /(atom sec) and 2.65 ± 0.04 x 10-11 cm3 /(atom sec) for He and Ar, respectively. The current results are placed in context with similar rates for other alkali-rare gas collision pairs using adiabaticity arguments. Pulsed excitation on the two-photon Cs 6 2S1/2 → 8 2D3/2, 5/2 transition results in time-resolved fluorescence at 601 nm. The rates for fine structure mixing between the 8 2D3/2, 5/2 states have been measured for helium and argon rare gas collision partners. The mixing rates are very fast, 2.6 ± 0.2 x 10-9 cm3/(atom s) for He and 5.2 ± 0.4 x 10-10 cm3/(atom s) for Ar, about 2-3 times faster than for the Cs 7 2D5/2 ↔ 7 2D3/2 relaxation. The quenching rates are also rapid, 1.07 ± 0.04 x 10-10 cm3/(atom s) and 9.5 ± 0.7 x 10-11 cm3/(atom s) for He and Ar, respectively. The rapid fine structure rates are explained by the highly impulsive nature of the collisions and the large average distance of the valence electron from the nucleus. Quenching rates (intermultiplet transfer) are likely enhanced by the closely spaced, 9 2P levels. Stimulated emission on the ultraviolet and blue transitions in Cs has been achieved by pumping via two-photon absorption for the pump transition 62S 1/2 → 72D5/2,3/2. The performance of the optically-pumped cesium vapor laser operating in ultraviolet and blue has been extended to 650 nJ/pulse for 387 nm, 1.3 µJ/pulse for 388 nm, 200 nJ/pulse for 455 nm and 500 nJ/pulse for 459 nm. Emission performance improves dramatically as the cesium vapor density is increased and no scaling limitations associated with energy pooling or ionization kinetics have been observed.

AFIT Designator

AFIT-ENP-DS-18-M-076

DTIC Accession Number

AD1056242

Download

Share

COinS