Level-crossing field

Thus, the S-T conversion rate increases suddenly at the level-crossing field (B = Buz) through the HFC term of Eq. (3-13b). 

In this case, the S-T conversion suddenly occurs at the level-crossing field (5lc) as shown in Fig. 6-1(c). When a reaction occur from an S-precursor, the S-T conversion rate is increased by a magnetic field at Blc. Thus, the Yc (B) value is decreased by Blc and the Ye (B) value is increased by it. When a reaction occur from a T-precursor, the T-S... 

Table 8-1. Level-crossing fields (Bmax/mT = gix/mT) observed for biradicals...

Fig. 1. Schematic for /zSR and fiLCR experiments. For pSR the muon spin polarization vector starts off in the x direction (open arrow). It then precesses about an effective field (the vector sum of the external field and the internal hyperfine field), which is normally approximately the z direction. The muons are detected in the M counter, and positrons from muon decay are detected in the L or R counters. For pLCR, the muon spin polarization is initially along the external field or t axis (solid arrow). The positron rates in the F and B counters are measured as a function of external field. A sharp decrease in the asymmetry of the F and B counting rates signifies a level crossing.

Consider for example the simplest possible system consisting of the muon, an electron, and a single spin nucleus labelled i = n. Take the muon and nuclear hyperfine interactions to be istoropic. The level crossing of interest occurs near the field... 

The second point made by Fig. 6.2, although not with very high resolution, is that the levels of n and n + 1 cross. The extreme m = 0 red and blue states have Stark shifts of approximately 3n2E/2, which combined with the n — (n + 1) energy spacing of 1/n3, yields a crossing field of... 

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