Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - The breakdown of superfluidity in liquid 4He. II : an investigation of excitation emission from negative ions travelling at extreme supercritical velocities.
AU - Ellis, T.
AU - McClintock, Peter V. E.
AU - Bowley, R. M.
AU - Allum, D. R.
PY - 1980/4/18
Y1 - 1980/4/18
N2 - We have measured the drift velocity, v, of negative ions in He II at a temperature of 0.34 K and a pressure of 25 bar for electric fields, E, in the range 5 x 10^3 < E < 6 X 10^6 V/m. For if v < 70 m/s, the results are in good agreement with the predictions of the roton pair-emission theory of Bowley and Sheard. Even better agreement is obtained by extending the theory to take explicit account of departures from parabolicity of the real dispersion curve at large momenta, variations in the pole strength of high momentum excitations, and the slight increase in the average momentum of excitations emitted at large values of v. For v > 70 m/s, however, experiment and theory are in clear disagreement: by if = 80 m/s, the measured drag on the ion has become about 100% larger than the theoretical prediction. We tentatively attribute this discrepancy to the onset at if ~ 70 m/sl of a new and, so far, unidentified dissipation mechanism.
AB - We have measured the drift velocity, v, of negative ions in He II at a temperature of 0.34 K and a pressure of 25 bar for electric fields, E, in the range 5 x 10^3 < E < 6 X 10^6 V/m. For if v < 70 m/s, the results are in good agreement with the predictions of the roton pair-emission theory of Bowley and Sheard. Even better agreement is obtained by extending the theory to take explicit account of departures from parabolicity of the real dispersion curve at large momenta, variations in the pole strength of high momentum excitations, and the slight increase in the average momentum of excitations emitted at large values of v. For v > 70 m/s, however, experiment and theory are in clear disagreement: by if = 80 m/s, the measured drag on the ion has become about 100% larger than the theoretical prediction. We tentatively attribute this discrepancy to the onset at if ~ 70 m/sl of a new and, so far, unidentified dissipation mechanism.
U2 - 10.1098/rsta.1980.0195
DO - 10.1098/rsta.1980.0195
M3 - Journal article
VL - 296
SP - 581
EP - 595
JO - Philosophical Transactions of the Royal Society of London A
JF - Philosophical Transactions of the Royal Society of London A
SN - 0264-3820
IS - 1425
ER -