Infrared picosecond transient hole-burning studies of the effect of hydrogen bonds on the vibrational line shape

With infrared transient hole-burning spectroscopy we have investigated the influence of OD ... X hydrogen bonds on the vibrational line shape of O-D stretch vibrations in acid zeolites. The effect of hydrogen bonding on the line shape depends critically on the type of hydrogen bond. For hydrogen bonding in a rigid structure, the hydrogen bond determines the inhomogeneous linewidth, but the homogeneous linewidth is determined by coupling to a similar to 200 cm(-1) lattice mode as concluded from the temperature dependence of the dephasing rate. When the hydrogen bond is formed with an adsorbing molecule, the coupling between the high-frequency O-D stretch vibration and the low-frequency OD ... X hydrogen-bond stretching mode does determine the homogeneous linewidth. The difference between the two systems can be explained by the different hydrogen-bond potentials. Variation of the adsorbate provides a means of obtaining conclusive information on the coupling mechanism between the high-frequency O-D stretching mode and the low-frequency OD ... X hydrogen-bond stretching mode. (C) 1996 American Institute of Physics.