Vibrational overtone spectroscopy of the 4νOH+νOH’ combination level of HOOH via sequential local mode–local mode excitation

Sequential pumping of the local OH stretch vibrations in hydrogen peroxide using infrared-optical double resonance permits spectroscopic access to the 4-nu(OH) + nu(OH)' combination level. Analysis of the rotationally resolved vibrational overtone spectra generated by this technique determines approximate rotational constants for this level and a value of 17 051.8 +/- 3.4 cm-1 for the O-O bond dissociation energy. The linewidths of individual zeroth-order rotational transitions increase sharply with increasing K and change from smooth Lorentzian profiles to clumps of individual lines. The K dependence of the clump widths suggests that an a-axis Coriolis interaction is the primary coupling mechanism between the zeroth-order bright state and dark bath states. As a function of increasing J, each clump coalesces into a smooth Lorentzian profile. We interpret this J dependence in terms of a model that includes rotationally induced vibrational coupling among zeroth-order dark states.