Lande factors for the states

The above approach is, however, not applicable to the most frequent case, namely to that of non-excited molecules in the 1S state, in which both the electronic and spin magnetic moments axe absent. The reasons for the appearance of a non-zero magnetic moment of the rotating molecule, disregarded in (4.55)-(4.59) axe as follows. Firstly, it is the contribution of nuclear / , connected with the rotation of the nuclear core of the linear molecule [80, 87, 294, 319, 321, 322, 395, 396]. For a diatomic molecule the contribution of nuclear rotation can be estimated from the simple expression  

In order to give an idea of these effects, let us consider in greater detail a concrete case of a hydrogen-like molecule, in particular the test molecule Na2 (see Fig. 4.25). In order to evaluate g1 from (4.60) we will consider that the structure of an alkali dimer is completely hydrogenlike, in other words, that only the valence electron participates in the formation of the molecule, and one may assume, following [87], that Z is close to unity. Thus, gj is always positive and does not, in such approximations, depend on v, J and on the electronic term. For alkali dimers the values of g1, as 

Let us now consider the second mechanism, namely, the appearance of the electronic contribution gj due to the interaction with the paramagnetic electronic states. In particular, the singlet terms 1II and of one parity (either u u or g - g) interact because of the non-zero matrix elements of the electron-rotation operator [—l/(2/iro)](J+L- + J L+), where // is the reduced mass, ro is the internuclear distance (in atomic units) and the cyclic components of the vectors are defined in the same way as in [267] = Lx iLy, = Jx iJy connecting the x and y 

in spite of the large variety of situations, we hope that the above brief information on molecular magnetic moments, as well as the concrete examples discussed, might be of use in estimating the nature and 

---