Methods to investigate IVR:

Three methods have been been used to investigate the intramolecular redistribution of vibrational enery (IVR):

• High resolution IR spectroscopy
  From the analysis of the molecular spectra a molecular Hamiltonian H_mol is obtained and the time evolution of the wave function Ψ(t) is then given by the solution of the corresponding time dependent Schrödinger equation [1-4].
• Femtosecond/picosecond pump-probe experiments
  The process of intramolecular vibrational energy redistribution can be followed directly in a time resolved pump-probe experiment. The progress of IVR is followed by a probe pulse measuring the infrared absorption [5], ultraviolet absorption [6-10] or a multiphoton ionization signal [11,12].
• The intramolecular relaxation can be obtained also theoretically from numerical caculations of the molecular quantum dynamics on an ab initio potential surface [13,14].

In our lab we have set up an experiment to investigate IVR in the gas phase by the femtosecond pump-probe technique with 100 fs laser pulses applying either UV- or IR-absorption in the probe step. To improve the sensitivity of our experiments the pump- and the probe beam are coupled to a capillary with an inner diameter of 0.2 mm and a length of 500 mm.

References:

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