Aspects on Rotational Cooling of Glyoxal Using Carrier Gases He and Ar

Molecular beam characterization performed for the carrier gases He and Ar reveals particularities in glyoxal fluorescence signal and beam rotational temperature related to the carrier gas. The dependence of the fluorescence signal on stagnation pressure at constant glyoxal partial pressure shows that the signal has a maximum that is higher for He than for Ar. The estimation of the effective nozzle diameter, deff, for different stagnation pressure values, p0, suggests that the decrease of the fluorescence intensity at higher p0 can be attributed, at least in part, to deff. On the other hand, Ar has the higher rotational cooling efficiency. Also the results show that the velocity slip (i.e. the difference between the mean velocities of the species in the binary mixture expansion) between glyoxal and carrier gas is not responsible for the difference in rotational cooling efficiencies of He and Ar.

A summary of results obtained with the cryogenic electrostatic storage ring DESIREE

This paper highlights results from recent studies of cryogenically cooled atomic and molecular anions carried out at the DESIREE storage ring facility at Stockholm University in Stockholm, Sweden. These results include measurements of lifetimes of excited metastable states in atomic anions (S−, Se−, Te−, Ni−, and Pt−), pilot studies of rotational cooling of OH−, and cooling and decay of cluster anions exemplified by results for Ag5−.

The maximum coefficient of performance (COP) of vortex tubes

In a number of recent publications, it has been shown that the vortex tube effect occurs as a result of the extraction of work from a radial inflow of rotating gas. The delivered energy and its corresponding temperature drop have been derived from first principles. This work studies the cycle of rotational cooling by also considering the process of gas compression and arrives at the maximum theoretical value of the coefficient of performance (COP). For air, the maximum COP of the vortex tube effect is 2.5; it can reach over 15.0 for common refrigerants (e.g., R-218) and 20.0 or higher for other gases (e.g., n-heptane).