Positron annihilation in low-temperature rare gases. II. Argon and neon
Lifetime measurements of slow-positron and ortho-positronium (o-Ps) annihilation were made in argon and neon gases at room temperature and below. The argon experiments cover the temperature range 115 to 300$sup 0$K and the density range 0.0356 to 0.0726 g/cm$sup 3$ (approximately equal to 20 to 40 amagat). The slow-positron spectra in argon exhibit a departure from free- positron annihilation below 200$sup 0$K. The departure becomes more marked as the temperature is lowered. No deviation from free o-Ps pickoff annihilation is observed in argon at low temperatures. The neon measurements cover the temperature range 30 to 300$sup 0$K and the density range 0.032 to 0.89 g/cm$sup 3$ (approximately equal to 35 to 980 amagat). No effect of temperature on the slow-positron spectra throughout the temperature and density ranges investigated in neon is observed. The spectra are very exponential with a corresponding decay rate which is temperature as well as time independent and is directly proportional to density over the ranges investigated. The o-Ps data are more eventful in that the o-Ps lifetime at near-liquid densities is approximately 20 nsec, a factor of nearly 4 greater than the value obtained using the pickoff- annihilation coefficient obtained at lower densities. This is evidence for positronium-induced cavities in low-temperature neon. A brief discussion of the argon and neon results is given in the context of the explanations offered for the low-temperature effects observed in helium gas. (auth)
- Research Organization:
- Wayne State Univ., Detroit
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-33-008288
- OSTI ID:
- 4149160
- Journal Information:
- Phys. Rev., A, v. 12, no. 2, pp. 386-395, Other Information: Orig. Receipt Date: 30-JUN-76
- Country of Publication:
- United States
- Language:
- English
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640303* -Physics Research-Atomic
Molecular & Chemical Physics-Positronium
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*ARGON- POSITRON COLLISIONS
*NEON- POSITRON COLLISIONS
*POSITRON COLLISIONS- ANNIHILATION
DECAY
GASES
LIFETIME
LOW TEMPERATURE
RARE GASES