Ultrafast pump–probe spectroscopy of strongly hydrogen-bonded hydrogen fluoride–pyridine complexes

We present a study on the vibrational dynamics of the HF/FHF stretch combination vibration of HF–pyridine complexes in diluted pyridine solution. The relaxation of the excited vibration is observed to occur in two steps. In the first step, energy is transferred from the excited combination vibration to the hydrogen bond F–H⋯F modes with a time constant of 0.51±0.09 ps. In a second relaxation process these hydrogen bond modes decay with a time constant of 2.6±0.3 ps.