  A theoretical scheme for the analysis of experimental data on IR spectroscopy
for a quantum particle in a double well potential (DWP) is suggested. The
analysis is based on the trigonometric DWP for which the exact analytic
solution of the Schr\"odinger equation is available. The corresponding energy
levels along with their wave functions are expressed via special functions
implemented in {\sl {Mathematica}} (spheroidal function and its spectrum of
eigenvalues). As a result trigonometric DWP makes the calculation of the energy
levels an extremely easy procedure. It contains three parameters allowing one
to model the most important characteristics of DWP (barrier height and the
distance between the minima of the potential) along with the required
asymmetry. Our approach provides an accurate calculation of the energy spectrum
for hydrogen bonds in chromous acid (CrOOH) and potassium dihydrogen phosphate
(${\rm{KH_2PO_4}}$) along with their polarizability in agreement with available
experimental data.
