Density and temperature dependencies of ortho-positronium annihilation rates in ethane gas

Sharma, S. C.; McNutt, J. D.; Eftekhari, Abe; Hejl, R. A.

doi:10.1063/1.442171

Cited by 13 publications

(6 citation statements)

References 11 publications

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“…The corrected values of the normalized decay rate, q (T ), for all of the gases used in this experiment are plotted as a function of temperature in figure 2. One clear feature in all these data is that q (T ) increases with temperature in contrast to the previous constant results for ethane [18], methane [12], neon [14], argon [13], nitrogen [11] and helium [16], but in nominal agreement with the second helium result [17]. Since most of these previous data were taken at temperatures of less than 300 K, direct comparison of quenching results obtained over different temperature ranges may not be appropriate.…”

Section: Discussionmentioning

confidence: 62%

Temperature dependence of positronium decay rates in gases

Vallery

Leanhardt

Skalsey

et al. 2000

J. Phys. B: At. Mol. Opt. Phys.

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The decay rate of orthopositronium (o-Ps) formed and thermalized in eight different gases is systematically investigated as a function of temperature. The o-Ps collisional quenching rate is observed to increase with temperature, T , for He, Ne, Ar, N 2 , ethane, methane, isobutane and neopentane. All of the gases except ethane and methane increase linearly over the investigated temperature range, 300 K < T < 600 K. Recent theoretical work for noble gases at elevated temperatures suggests a linear increase in the collisional quenching rate with temperature at the low densities used herein where collective phenomena such as bubble formation and density fluctuations are not present. When comparisons can be made with previous experimental results the agreement is generally poor. Precision o-Ps decay rate measurements using gases are also discussed concerning systematic effects due to the energy dependence of the collisional quenching rate.

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Section: Discussionmentioning

confidence: 62%

Temperature dependence of positronium decay rates in gases

Vallery

Leanhardt

Skalsey

et al. 2000

J. Phys. B: At. Mol. Opt. Phys.

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“…(1) with a X Z ef{ =0.625± 0.020. *Z e ff has recently been observed to decrease with increasing temperature of ethane gas between 256 and 377 K. 2 Following this observation, a linear dependence of x Z eff with temperature has been assumed. The values of A 0 _ Ps measured for ethane densities higher than about 11 amagat deviate significantly from those values calculated from Eq.…”

Section: Sensitivity Of Orthopositronium Annihilation Rates To Densitmentioning

confidence: 95%

“…(4) to data available for A O _ PS at temperatures both near and far from the critical temperature of ethane, we have examined the recent A 0 > Ps data at the highest temperature, 377 K, investigated in the present series of experiments. 2 The measured values of AA in ethane at 377 K are plotted as a function of D(kTK 0 ) l/2 in Fig. 4.…”

Section: Sensitivity Of Orthopositronium Annihilation Rates To Densitmentioning

confidence: 99%

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Sensitivity of Orthopositronium Annihilation Rates to Density Fluctuations in Ethane Gas

1982

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In this Letter we present results from a continuing series of experiments whereby positron annihilation techniques are used to investigate the influence of density fluctuations on the annihilation of orthopositronium (o-Ps) atoms formed in ethane gas. We present new results that are the first to show a complex dependence of orthopositronium annihilation rates (x o -Ps ) on the density of the gas over a wide range of densities at a temperature that is only about 1 K above the critical temperature of the gas. These results support the sensitivity of A 0 _ Ps to density fluctuations in ethane gas and allow us to study the application of a simple density fluctuation model to X 0 . Ps at sufficiently high densities of the gas that density fluctuations are expected to be large and highly correlated. The behavior of o-Ps annihilation rates has been reported recently as a function of density and temperature in methane 1 and ethane 2 gases. However, these measurements were made only for limited ranges of densities and temperatures of the gases. Nevertheless, they have indicated that the annihilation rates of o-Ps atoms in methane and ethane gases are sensitive to density fluctuations. Generally at low densities, o-Ps annihilation rates increase linearly with the density of the gas up to certain temperature-dependent values of gas density Orthopositronium annihilation rates have been measured in ethane gas for densities in the range 1.8 to 286 amagats at 306.4 K. The behavior of the measured annihilation rates at densities up to about 70 amagats can be explained in terms of a simple density fluctuation model. New features are observed at higher densities of ethane at 306.4 K.

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“…Thus the above stability condition needs to be joined with additional statements which require that spontaneous energy and density fluctuations within the gas will not destroy the trapped state. These points are taken up below.The 0-Ps decay rate for densities p o < p * is given by(Sharma and McNutt 1981, Sharma et a1 1981, Iakubov and Khrapak 1982…”

mentioning

confidence: 99%

Transition to collective behaviour of a quantum particle in a classical gas

Miller

Lehtihet

Kowalski

et al. 1989

J. Phys. B: At. Mol. Opt. Phys.

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Measurements of the decay rate of orthopositronium in dilute ethane and methane gas are interpreted within the context of three different models. In the first it is assumed that the 0-Ps atom becomes trapped in a bubble which it creates. In the second it is assumed that the 0-Ps atom passively samples 'frozen' density fluctuations in the host fluid in the absence of self-trapping. In the third, due to McNutt and Sharma, it is assumed that the 0-Ps atom only samples regions of reduced density. A number of criteria are developed to test each hypothesis. Rough estimates based on sample data for ethane favour the second approach.

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Density and temperature dependencies of ortho-positronium annihilation rates in ethane gas

Cited by 13 publications

References 11 publications

Temperature dependence of positronium decay rates in gases

Temperature dependence of positronium decay rates in gases

Sensitivity of Orthopositronium Annihilation Rates to Density Fluctuations in Ethane Gas

Transition to collective behaviour of a quantum particle in a classical gas

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