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Boltzmann Entropy of a Freely Expanding Quantum Ideal Gas

Saurav Pandey, Junaid Majeed Bhat, Abhishek Dhar +5 more

arXiv:2303.12330Journal of Statistical PhysicsAug 15, 202314 citations

Emergence of quantum effects in a gas

WORLD SCIENTIFIC eBooksSep 1, 20110 citations

Some macroscopic quantum effects in rarefied molecular gases

A. S. Bruev

Журнал Экспериментальной и Теоретической ФизикиJan 1, 19860 citations

THE SIGNIFICANCE OF COMPRESSION SHOCKS IN THE PRODUCTION OF INTENSE MOLECULAR BEAMS WITH NOZZLES

K. Bier, O. F. Hagena

S>In the production of intensive molecular beams using nozzles, compression shocks must be avoided as much as possible since they cause a broadening of the velocity distribution and a reduction of the particle current density of the molecular beam. The conditions for the occurrence and the effect of such compression shocks was investigated by measurement of the velocity distribution and the beam intensity for the case when a convergent nozzle is used for the beam production. It was shown that under given conditions a strong compression shock connected with the collision system of the freely expanding gas beam occurs. This compression reduces the beam intensity in single-molecule beams by an order of magnitude and in condensed beams by two orders of magnitude. When this strong compression shock released from the first beam stop is avoided by a suitable selection of the research conditions, weak compression shocks emanating from the peeler can still occur. Possible reduction of this weak compression shock is discussed. (tr-auth)S>In the production of intensive molecular beams using nozzles, compression shocks must be avoided as much as possible since they cause a broadening of the velocity distribution and a reduction of the particle current density of the molecular beam. The conditions for the occurrence and the effect of such compression shocks was investigated by measurement of the velocity distribution and the beam intensity for the case when a convergent nozzle is used for the beam production. It was shown that under given conditions a strong compression shock connected with the collision system of the freely expanding gas beam occurs. This compression reduces the beam intensity in single-molecule beams by an order of magnitude and in condensed beams by two orders of magnitude. When this strong compression shock released from the first beam stop is avoided by a suitable selection of the research conditions, weak compression shocks emanating from the peeler can still occur. Possible reduction of this weak compression shock is discussed. (tr-auth)

Nov 1, 19620 citations

Probing Phase Fluctuations in a 2D Degenerate Bose Gas by Free Expansion

Jae-yoon Choi, Sang Won Seo, Woo Jin Kwon +1 more

We measure the power spectrum of the density distribution of a freely expanding two-dimensional (2D) degenerate Bose gas, where irregular density modulations gradually develop due to initial phase fluctuations in the sample. The spectrum has an oscillatory shape, where the peak positions are found to be independent of temperature and show scaling behavior in the course of expansion. The relative intensity of phase fluctuations is estimated from the normalized spectral peak strength and observed to decrease at lower temperatures, confirming the thermal nature of the phase fluctuations. We investigate the relaxation dynamics of nonequilibrium states using the power spectrum. Free vortices are observed with ring-shaped density ripples in a perturbed sample after a long relaxation time.We measure the power spectrum of the density distribution of a freely expanding two-dimensional (2D) degenerate Bose gas, where irregular density modulations gradually develop due to initial phase fluctuations in the sample. The spectrum has an oscillatory shape, where the peak positions are found to be independent of temperature and show scaling behavior in the course of expansion. The relative intensity of phase fluctuations is estimated from the normalized spectral peak strength and observed to decrease at lower temperatures, confirming the thermal nature of the phase fluctuations. We investigate the relaxation dynamics of nonequilibrium states using the power spectrum. Free vortices are observed with ring-shaped density ripples in a perturbed sample after a long relaxation time.

arXiv:1206.2232Physical Review LettersSep 19, 201234 citations

Emerging Quantum Order in an Expanding Gas

Lev Vidmar, J. P. Ronzheimer, Michael Schreiber +6 more

Jan 1, 20150 citations

Occurrence of quantum effects during rotational relaxation of a freely expanding gas

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