Lowhyphen;Pressure Senftleben Effects for Molecular Oxygen

摘要

The effect of a magnetic field on the thermal conductivity and viscosity coefficients of paramagnetic Hund's case (b) multipletSgr;molecules, and in particular3Sgr;oxygen, is investigated theoretically for the lowhyphen;pressure region, where the effects are functions ofHthinsp;sol;thinsp;p. In this region the fields involved are correspondingly low, so that the total angular momentumJis well defined, and the distributionhyphen;function density matrix may be assumed to commute withJ2. This fact is exploited in the solution of the kinetic equation. The present treatment makes only very weak assumptions about the nature of the collisions, basically only that the collision (super)operatorRis spin independent, which makes it possible to choose a basis in which theRmatrix is diagonally dominant. Through detailed analysis of the dependence of all quantities involved on the mean rotational quantum number,Nthinsp;equals;thinsp;lang;lsqb;Nlpar;Nthinsp;plus;thinsp;1rpar;rsqb;1sol;2rang;, information about the transport coefficients is obtained in a manner independent of the precise structure of the collision matrix. It is shown that the transport coefficients can be represented as series in powers ofNminus;2, and sinceNminus;2is small, even at liquidhyphen;nitrogen temperature, this suggests that the leading terms are the only significant ones. For3Sgr;molecules such as oxygen, the even effects show a structure which is a simple superposition of two features of the type found in diamagnetic molecules, one at low field associated primarily withJthinsp;equals;thinsp;Nthinsp;plusmn;thinsp;1, and the other at high field, associated primarily withJthinsp;equals;thinsp;N. This formal result depends on very few assumptions aboutR, whereas the exact positions and intensities depend on the detailed values of theRhyphen;matrix elements. The observed 2:1 intensity ratio is consistent with the assumption thatRis equivalent within anNshell to a unit superoperator, but this assumption, while sufficient, is not necessary. The odd effects also show a twohyphen;feature structure. The highhyphen;field feature is again of simple diamagnetic type, while the lowhyphen;field feature is of reduced intensity, and in general of more complex form.