© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

Physical Review

Trapping Lifetime of Negative Ions in Rotating Superfluid Helium Under Pressure

William P. Pratt, William Zimmermann

Published Jan 5, 1969• 69 citations

Abstract

Measurements have been made of the lifetime for the escape of negative ions trapped in rotating helium II as a function of temperature and pressure. These measurements concern lifetimes in the range from 10 to 1000 sec, and have been made between the temperatures of 1.09 and 1.68\ifmmode^\circ\else\textdegree\fi{}K from the vaporization pressure to the solidification pressure. At constant pressure the lifetime decreases rapidly with increasing temperature. The curves of constant lifetime in the pressure-versus-temperature plane have negative slopes $\frac{\mathrm{dP}}{\mathrm{dT}}$ and positive second derivatives $\frac{{d}^{2}P}{d{T}^{2}}$. The results have been interpreted in terms of the bubble model of the negative ion and the vortex-line model of the rotating superfluid. The interpretation suggests that the ion radius equals approximately 19.5 A at saturated vapor pressure and decreases to a value between 12 and 14 \AA{} at the solidification pressure. However, a significant discrepancy between theory and experiment casts some doubt on the radius values obtained.

DOI: 10.1103/physrev.177.412

Related papers

Mobility of Negative Ions Along Vortices in Rotating Superfluid Helium

Roger L. Douglass

The mobility of negative ions trapped on linear vortices in rotating superfluid helium has been measured by a time-of-flight technique in the temperature range $0.8\ifmmode^\circ\else\textdegree\fi{}\mathrm{K}<T<1.6\ifmmode^\circ\else\textdegree\fi{}\mathrm{K}$. Measurements could not be extended below 0.8\ifmmode^\circ\else\textdegree\fi{}K because, contrary to the present theory, the ion escape rate became too large. No evidence of direct trapping of positive ions by vortex lines was observed down to 0.4\ifmmode^\circ\else\textdegree\fi{}K. The trapped-ion mobility is interpreted in terms of scattering of the ion by thermal distributions of quantized vortex waves and rotons localized about the vortex axis.

Physical Review•Oct 5, 1968•56 citations

Positive-Ion Trapping on Vortex Lines in Rotating He II

Gary A. Williams, Keith DeConde, R. E. Packard

The direct trapping of positive He ions on quantized vortex lines in rotating He II has been observed at temperatures below 0.7 K. Trapping lifetimes have been measured between 0.1 and 0.7 K, and agree with models of thermal escape and charge loss from vortex motion. An ion radius of 7.7\ifmmode\pm\else\textpm\fi{}0.1 \AA{} is found.

Physical Review Letters•Apr 14, 1975•52 citations

Trapping of Negative Ions in Turbulent Superfluid Helium

Donald M. Sitton, Frank Moss

Capture and escape of negative ions by vorticity resulting from a supercritical heat current in liquid He II are demonstrated in the temperature range between 1.6 and 1.8\ifmmode^\circ\else\textdegree\fi{}K. The vorticity is identical to that produced by rotation except for configuration of the individual lines. The escape probability was measured between 1.7 and 1.8\ifmmode^\circ\else\textdegree\fi{}K and is in agreement with the theory of Donnelly.

Physical Review Letters•Nov 10, 1969•44 citations

Negative-Ion Capture by Vortex Lines in Helium II

D. J. Tanner

We have studied negative-ion absorption by rotating He II from 0.98\ifmmode^\circ\else\textdegree\fi{}K to 1.7\ifmmode^\circ\else\textdegree\fi{}K. Measurements of vortex-line capture cross sections are reported as a function of temperature (0.98\ifmmode^\circ\else\textdegree\fi{}K to 1.7\ifmmode^\circ\else\textdegree\fi{}K at three electric fields (16.3, 49.0, and 97.9 V/cm) and as a function of electric field (10 to 200 V/cm) at two temperatures. Great care was taken to insure that the reported cross-section values were not affected by space-charge effects. The results are found in good agreement with the ion-capture theories developed by Donnelly and Roberts. The decrease in cross section above 1.6\ifmmode^\circ\else\textdegree\fi{}K is in agreement with the escape calculation of Parks and Donnely and supports their value of 15.96 \AA{} for the negative-ion radius.

Physical Review•Dec 2, 1966•58 citations

Capture Width of Vortex Lines for Negative Ions in Helium II

Roger L. Douglass

Negative-ion trapping has been investigated in rotating liquid helium at temperatures above 1.2\ifmmode^\circ\else\textdegree\fi{}K. We report measurements of the ion-capture width versus temperature and electric field (from 5 to 100 V/cm). The theory of the effect is reviewed and discussed and is shown to be in excellent agreement with experiment. Owing mainly to the insensitivity, at low ratios of electric field to temperature, of the capture width to the properties of the ion-vortex potential well, we are able to deduce only that the well must be larger than the ionic mean free path.

Physical Review•Jan 7, 1966•47 citations

Effect of He3 Impurities on the Lifetime of Ions Trapped on Quantized Vortex Lines

Gary A. Williams, R. E. Packard

The lifetimes of both positive and negative ions trapped on quantized vortex lines in rotating $^{3}\mathrm{He}$-$^{4}\mathrm{He}$ mixtures have been measured at temperatures down to 0.1 K. Evidence is found that the $^{3}\mathrm{He}$ condenses at the vortex core, and possibly at the surface of the electron bubble.

Physical Review Letters•Jul 28, 1975•44 citations

Measurements have been made of the lifetime for the escape of negative ions trapped in rotating helium II as a function of temperature and pressure. These measurements concern lifetimes in the range from 10 to 1000 sec, and have been made between the temperatures of 1.09 and 1.68\ifmmode^\circ\else\textdegree\fi{}K from the vaporization pressure to the solidification pressure. At constant pressure the lifetime decreases rapidly with increasing temperature. The curves of constant lifetime in the pressure-versus-temperature plane have negative slopes

\frac{\mathrm{dP}}{\mathrm{dT}}

and positive second derivatives

\frac{{d}^{2}P}{d{T}^{2}}

. The results have been interpreted in terms of the bubble model of the negative ion and the vortex-line model of the rotating superfluid. The interpretation suggests that the ion radius equals approximately 19.5 A at saturated vapor pressure and decreases to a value between 12 and 14 \AA{} at the solidification pressure. However, a significant discrepancy between theory and experiment casts some doubt on the radius values obtained.

The mobility of negative ions trapped on linear vortices in rotating superfluid helium has been measured by a time-of-flight technique in the temperature range $0.8\ifmmode^\circ\else\textdegree\fi{}\mathrm{K}<T<1.6\ifmmode^\circ\else\textdegree\fi{}\mathrm{K}$. Measurements could not be extended below 0.8\ifmmode^\circ\else\textdegree\fi{}K because, contrary to the present theory, the ion escape rate became too large. No evidence of direct trapping of positive ions by vortex lines was observed down to 0.4\ifmmode^\circ\else\textdegree\fi{}K. The trapped-ion mobility is interpreted in terms of scattering of the ion by thermal distributions of quantized vortex waves and rotons localized about the vortex axis.

We have studied negative-ion absorption by rotating He II from 0.98\ifmmode^\circ\else\textdegree\fi{}K to 1.7\ifmmode^\circ\else\textdegree\fi{}K. Measurements of vortex-line capture cross sections are reported as a function of temperature (0.98\ifmmode^\circ\else\textdegree\fi{}K to 1.7\ifmmode^\circ\else\textdegree\fi{}K at three electric fields (16.3, 49.0, and 97.9 V/cm) and as a function of electric field (10 to 200 V/cm) at two temperatures. Great care was taken to insure that the reported cross-section values were not affected by space-charge effects. The results are found in good agreement with the ion-capture theories developed by Donnelly and Roberts. The decrease in cross section above 1.6\ifmmode^\circ\else\textdegree\fi{}K is in agreement with the escape calculation of Parks and Donnely and supports their value of 15.96 \AA{} for the negative-ion radius.

Negative-ion trapping has been investigated in rotating liquid helium at temperatures above 1.2\ifmmode^\circ\else\textdegree\fi{}K. We report measurements of the ion-capture width versus temperature and electric field (from 5 to 100 V/cm). The theory of the effect is reviewed and discussed and is shown to be in excellent agreement with experiment. Owing mainly to the insensitivity, at low ratios of electric field to temperature, of the capture width to the properties of the ion-vortex potential well, we are able to deduce only that the well must be larger than the ionic mean free path.

The lifetimes of both positive and negative ions trapped on quantized vortex lines in rotating

^{3}\mathrm{He}

-

^{4}\mathrm{He}

mixtures have been measured at temperatures down to 0.1 K. Evidence is found that the

^{3}\mathrm{He}

condenses at the vortex core, and possibly at the surface of the electron bubble.