Statistical and nonstatistical population of spin-orbit manifolds

3 Statistical and nonstatistical population of spin-orbit manifolds 

While in the photodissociation of H2O through the AlB state the two possible A-doublets of OH(2n) are populated in a highly nonstatistical way, the two spin-orbit states, 0H( n ) and 0H( n3/2), are perfectly statistically populated. Unlike for the A-doublets there is a priori no geometrical reason to expect a difference in the spin-orbit states other than that given by the 2j + 1 statistical weighting factor. Since j = N + 1/2 for 2n3/2 and j = N — 1/2 for 2n1/2, the statistical weighting factor is (N + l)/N. Therefore, the population ratio 2n3/2 / 2n1/2 multiplied by N/(N-1-1) must be 1 for a statistical distribution as it is indeed measured in the bulk, in the beam, as well as in the dissociation of single rotational states of H2O (Andresen and Schinke 1987). The reason for the statistical 

A preferential population of one spin-orbit state has been found for OH in the photodissociation of HONO, where the higher state is more populated than predicted by statistics (Vasudev, Zare, and Dixon 1984 Shan, Vorsa, Wategaonkar, and Vasudev 1989). In NO(2n) generated via photolysis of CH3ONO (Lahmani, Lardeux, and Solgadi 1986 Briihlmann, Dubs, and Huber 1987), (CHa NNO (Dubs, Briihlmann, and Huber 1986 Lavi and Rosenwaks 1988), or (CHa CONO (Schwartz-Lavi, Bar, and Rosenwaks 1986) the lower state is slightly more populated than the upper state. The reason for this preference is not yet clear. 

Another example of a dramatic difference in the population of the two spin-orbit states is the dissociation of HN3 in the electronic ground state induced by overtone pumping (Foy, Casassa, Stephenson, and King 1988  

---