Molecular spectroscopy and Bayesian spectral analysis—how many lines are there?

We demonstrate the Bayesian spectral analysis approach for analyzing neutron scattering molecular tunneling data. It is a generalized form of model fitting, which is appropriate when the number of parameters to be optimized is not known. Specifically, it addresses the question of how many excitation lines there is evidence for in the data. We review the theory of Bayesian spectral analysis relevant to our particular application, describe an efficient algorithm for its implementation, and illustrate its use with both simulated and real data. We believe that this powerful method of analysis will be a very useful tool in experimental molecular spectroscopy.