Dynamic Behavior of the Thermomagnetic Gas Torque
- 5 December 1969
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 188 (1), 433-444
- https://doi.org/10.1103/physrev.188.433
Abstract
The recently discovered thermomagnetic gas torque shows twofold behavior in the presence of a large modulating magnetic field collinear with the steady magnetic field. At steady fields of about one-half (the field for maximum torque), the torque is decreased by an amount if the modulation frequency is low compared to a collision frequency. As is increased, the torque returns to the value it had in the absence of modulation. From plots of versus , we have determined correlation frequencies for the collision processes. We find that, for high-enough pressure , varies linearly with for NO, , , and HD gases. However, it appears that although elastic collisions are the controlling process in the gas torque for NO, , and , inelastic collisions determine the gas-torque behavior for HD (at least for the low-field torque peak). At steady fields greater than , a precession-related phenomenon shows up as dispersionlike curves in plots of versus . For NO, such curves are observable at the molecular magnetic Larmor frequency and twice the Larmor frequency. From double-frequency curves, we obtain , in good agreement with Ramsey's value of -48.2. Although the dispersion curves cannot be resolved, precession-related phenomena are observable for , and HD. We can estimate that the values effective in the gas-torque phenomena are ∼ -10 and +1 for and HD. The value for agrees quite well with the average expected for molecules in fast rotational states (). The value for HD is in order-of-magnitude agreement with measurements of Ramsey.
Keywords
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