TRANSIENT-HOLE BURNING IN THE INFRARED-SPECTRUM OF A POLYMER WITH INTENSE PICOSECOND PULSES

Transient spectral holes of 70-cm-1 width are observed in the OH stretching band (3500 cm-1) of hydrogen-bonded poly(vinyl butyral) films at room temperature. The lifetime of the holes is measured to be T1=52 ps and interpreted as the population lifetime of the OH stretching vibration. Simultaneously inverse holes with a red shift of 21010 cm-1 and the same lifetime T1 are observed and explained by excited-state absorption. The inhomogeneous broadening of the OH absorption band presents direct evidence for site-specific frequency shifts of the hydrogen bridges. Breaking of H bonds and establishment of a new thermal equilibrium is indicated with time constant =155 ps by blue-shifted induced absorption around the monomeric-frequency position. © 1990 The American Physical Society.