Hello! Is there a place where I can find the expressions for higher order terms of molecular parameters (in particular the spin rotational parameter, ##\gamma##)? All the papers I find just show them up to second order. Thank you!
You can find the expressions for higher order terms of molecular parameters in various textbooks on molecular spectroscopy. A good starting point is the book Molecular Spectroscopy by J. Demaison, which contains a chapter on spin-rotation constants and their higher order terms. You can also find useful information in the Handbook of Molecular Constants by A.J. Merer, which includes tables of spin-rotation constants up to fourth order.