Infrared predissociation

Kidd, I.F. and Balint-Kurti, G.G. (1986). Infrared predissociation of the Ar-HD van der Waals complex, Faraday Discuss. Chem. Soc. 82, 241-250. 

C. Steinbach, P. Andersson, J. K. Kazimirski, U. Buck, V. Buch, and T. A. Beu, Infrared predissociation spectroscopy of large water clusters a unique probe of cluster surfaces, J. Phys. Chem. A 108, 6165-6174 (2004). 

Carrington A and McNab I R 1989 The infrared predissociation spectrum of H Accounts Chem. Res. 22 218-22... 

Figure 2. Section of the infrared predissociation spectrum of H+ recorded at high and low beam potentials.

The H+ infrared predissociation spectrum is so extensive that it is unlikely that a full assignment could ever be made the most that we can currently hope to achieve is an understanding of how such a spectrum could originate. An obvious first step to such an understanding would be to take a low resolution spectrum of the same region, in order to see whether any recognizable structure could be seen. Unfortunately our experiment has an inherently high resolution which prevents us... 

Figure 10 Infrared predissociation spectra of the HCO+ ionic core solvated by specific number of argon atoms.

For complexes such as Ar-H2, Ar-HF and Ar-lTCl, vibrational predissociation is a very slow process and does not cause appreciable broadening of the lines in the infrared spectmm. Indeed, for Ar-ITF, ITuang et al [20] showed that... 

Figure C 1.3.5. Spectra of two different infrared bands of HF dimer, corresponding to excitation of the bound (lower panel) and free (upper panel) HF monomers in the complex. Note the additional line width for the bound HF, caused by vibrational predissociation with a lifetime of about 0.8 ns. (Taken from 1211.)...

Howard, B.J. and Pine, A.S. (1985). Rotational predissociation and libration in the infrared spectrum of Ar-HCl, Chem. Phys. Lett. 122, 1-8. 

Nesbitt, D.J., Lovejoy, C.M., Lindemann, T.G., ONeil, S.V., and Clary, D.C. (1989). Slit jet infrared spectroscopy of NeHF complexes Internal rotor and. /-dependent predissociation dynamics, J. Chem. Phys. 91, 722-731. 

The assigment of the parent ion [FB(CD3OD)2] as the precursor of the fluoroanisole product has been clearly demonstrated by an infrared UV doubleresonance experiment. Here, the product ion signal is monitored as the infrared excitation is scanned. When the IR laser is in resonance with the C-O stretching of the methanol dimer within the 1-2 cluster, a decrease of the product signal is observed since the population of the parent ion decreases by the loss of one methanol molecule through the IR predissociation process (Brutschy et al. 1992). 

In regions of the spectrum where a tunable laser is available it may be possible to use it to obtain an absorption spectrum in the same way as a tunable klystron or backward wave oscillator is used in microwave or millimetre wave spectroscopy (see Section 3.4.1). Absorbance (Equation 2.16) is measured as a function of frequency or wavenumber. This technique can be used with a diode laser to produce an infrared absorption spectrum. When electronic transitions are being studied, greater sensitivity is usually achieved by monitoring secondary processes which follow, and are directly related to, the absorption which has occurred. Such processes include fluorescence, dissociation, or predissociation, and, following the absorption of one or more additional photons, ionization. The spectrum resulting from monitoring these processes usually resembles the absorption spectrum very closely. 

Graener H, Ye TQ, Laubereau A. Ultrafast vibrational predissociation of hydrogen bonds mode selective infrared photochemistry in liquids. I Chem Phys 1989 91 1043-1046. 

Schuder, M. D. and Nesbitt, D. J., High resolution near infrared spectroscopy ofHCl—DCl and DCl—HCl Relative binding energies, isomer conversion rates, and mode specific vibrational predissociation, J. Chem. Phys. 100,7250-7267 (1994). 

While no inelastic rotational cross-sections have as yet been reported for hydrogen colliding with Kr or Xe, McKellar (29) has measured a predissociation width of 0.11 cm for the (n,A,v,j,J)= (0,2,1,2,0) level of H2-Kr. As is apparently the case (see above) for H2 Ar, for which such widths have not yet been resolved, this value is somewhat (ca. 50%) larger than the prediction implied by the potential of Table I (see Table IV). Thus, it seems reasonable to expect that an analogously refined potential for H2 Kr could be obtdined from a simultaneous analysis of this observed level width and the discrete infrared spectrum. 

Hutson, J.M. "Vibrational Predissociation and Infrared Spectrum the Ar-HC Van der Waals Molecule", submitted to J. Chem. Phys. 

He-CO and He-HF complexes are very suitable systems to verify how well the theory that goes all the way from ab initio calculations of the in-termolecular potentials to line positions and intensities can reproduce the experimentally observed spectra. For both systems high-resolution infrared spectra have been recorded (67, 68). In addition, for He-HF also the rotational predissociation line widths have been measured (68). 

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