Edward R. Fisher

Alkali quenching in high temperature environments

Abstract The total cross section for the quenching of electronically excited alkali atoms by vibrationally excited N 2 is found to be insensitive to the vibrational level of the incident N 2 and to relative translational energy within the framework of the ionic intermediate quenching model. Thus, the discrepancy in measured cross sections between high temperature flame experiments and low temperature fluorescence measurements remains unresolved.

Vibrational relaxation by metal atoms

Abstract Estimates have been made on the vibrational relaxation of N 2 in collision with the metal atoms Li, Na, K, Rb, Cs and Al using an ionic curve crossing model. The relationship of these results to earlier calculations and to beam experiments are indicated.

Modeling of a pulsed CO/N2 molecular laser system

A detailed numerical model has been developed for characterizing the important energy‐transfer processes operative in the CO/N2 dc discharge laser system. The model is based upon a rate‐equation formulation which includes 30 levels of both CO and N2 and treats multiquantum electron‐molecule excitation processes, single‐quantum vibration‐vibration exchange and vibration‐translation energy‐transfer processes, and both harmonic and overtone spontaneous emission terms. In this paper the time evolution of the CO vibrational distribution with and without N2 is calculated, and the associated small‐signal gain is predicted and compared to the measurements of Jeffers and Wiswall. Good agreement is obtained between the predicted and measured delay times to maximum gain in a pulsed CO laser system for reasonable assumptions on the important system parameters. The variation in these predicted gains and time delays is explored for various values of the electron density, the translational‐rotational temperature, and th...

CO vibrational distributions to high levels in low‐pressure CO/He mixtures

Experimental measurement of the first‐ and second‐overtone spontaneous‐emissions spectrum in a low‐pressure CO/He plasma has enabled determination of the vibrational distribution up to v=30. The variation in the CO distribution as a function of CO and He partial pressure and plasma current has been correlated by a detailed model of the steady‐state energy‐transfer dynamics. The agreement between calculated and measured distributions has generated a consistent set of rate coefficients for CO/He mixtures for a temperature around 150 K.

A coefficients for spontaneous emission in CO

Simultaneous end light emission measurements of the first‐ and second‐overtone bands of CO have been obtained in a flowing CO‐N2‐He laser plasma. Interpretation of the band structure using A coefficients from Young and Eachus show consistent agreement with observation up to v=26. This agreement supports the use of these A coefficients in laser and kinetic applications.

CO vibrational distributions in the presence of oxygen

Direct measurements of the vibrational distribution to v?30 obtained from the first overtone emission from CO in a liquid‐N2‐cooled laser plasma have been made in the presence of varying amounts of O2. These observed distributions show enhanced vibrational populations for small additions and show upper‐level depopulation for larger additions. Both observations support a recent plasma‐kinetic model of the effect of O2 in low‐pressure CO laser plasmas.

Modeling of a pulsed CO/N2 molecular laser system. II. Effect of mixture components and temperature variation

The CO molecular laser model described in a previous publication has been used to investigate the effect of molecular mixture components and kinetic temperature variations on improving the gain of low‐lying CO infrared transitions. Gas mixtures involving diatomic molecules with both larger and smaller vibrational level spacing than CO are investigated. Vibrational pumping of CO by a molecule having a smaller vibrational spacing leads to negligible laser gain predictions due to the nonspecific nature of vibrational exchange processes. The largest predicted gain in the low‐lying transitions of CO is found for N2/CO mixtures at 77°K in which appreciable gain in the 2–1 transition is found.