Bug: NH2 g-factors

[mkelley]

As seen in a note to Fink & Hicks (1996) via Arpigny: only half the NH2 population contributes to the odd transitions (e.g., 0,8,0) and the other half contributes to the even transitions (e.g., 0,7,0). This was not accounted for in the g-factors of Tegler and Wyckoff (1989).

Verify and update accordingly.