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The Senftleben–Beenakker effect is the dependence on a magnetic or electric field of transport properties (such as viscosity and heat conductivity) of polyatomic gases. The effect is caused by the precession of the (magnetic or electric) dipole of the gas molecules between collisions. The resulting rotation of the molecule averages out the nonspherical part of the collision cross-section, if the field is large enough that the precession time is short compared to the time between collisions (this requires a very dilute gas). The change in the collision cross-section, in turn, can be measured as a change in the transport properties. The magnetic field dependence of the transport properties can also include a transverse component; for example, a heat flow perpendicular to both temperature gradient and magnetic field. This is the molecular analogue of the Hall effect and Righi-Leduc effect for electrons. A key difference is that the gas molecules are neutral, unlike the electrons, so the magnetic field exerts no Lorentz force. An analogous magnetotransverse heat conductivity has been discovered for photons 〔Geert L. J. A. Rikken, Anja Sparenberg, and Bart A. van Tiggelen, ''Photonic magneto-transport'', Physica B 246, 188 (1998).〕 and phonons.〔Cornelius Strohm, Geert L. J. A. Rikken, and Peter Wyder, ''Phenomenological evidence for the phonon Hall effect'', Phys. Rev. Lett. 95, 155901 (2005).〕 The Senftleben–Beenakker effect owes its name to the physicists Hermann Senftleben (Münster University, Germany) and Jan J. M. Beenakker (Leiden University, The Netherlands), who discovered it, respectively, for paramagnetic gases 〔Hermann Senftleben, ''Einfluss eines Magnetfeldes auf das Wärmeleitvermögen von paramagnetischen Gasen (of a magnetic field on the heat conductivity of paramagnetic gases )'', Phys. Z. 31, 822 (1930).〕 (such as NO and O2) and diamagnetic gases 〔Jan J. M. Beenakker, Giacinto Scoles, Hein F. P. Knaap, and Robert Maarten Jonkman, ''The influence of a magnetic field on the transport properties of diatomic molecules in the gaseous state'', Phys. Lett. 2, 5–6 (1962).〕 (such as N2 and CO). The change in the transport properties is smaller in a diamagnetic gas, because the magnetic moment is not intrinsic (as it is in a paramagnetic gas), but induced by the rotation of a nonspherical molecule. The importance of the effect is that it provides information on the angular dependence of the intermolecular potential. The theory to extract that information from transport measurements is based on the Waldmann-Snider equation (a quantum mechanical version of the Boltzmann equation for gases with rotating molecules). The entire field is reviewed in a two-volume monograph.〔Frederick R. W. McCourt, Jan J. M. Beenakker, Walter E. Köhler, and Ivan Kuščer, ''Nonequilibrium Phenomena in Polyatomic Gases'' (Oxford University Press, 1991).〕 ==See also== *Kinetic theory *Thermal Hall effect 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Senftleben–Beenakker effect」の詳細全文を読む スポンサード リンク
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