Although there have been many attempts using conventional CO2 lasers to carry out bond selective reactions by IR multiphoton excitation (IRMPE), none has been successful. The basic reason for this failure is that polyatomics do not absorb photons in the quasi-continuum {region of high density of states) fast enough compared with rates of intramolecular relaxation. By contrast, at low vibrational energies, energy is deposited mode-selectively in many polyatomics, but there are few reactions which occur at these low energies on ground state surfaces. Therefore, at the present time, bond selective processes induced by IRMPE may only be possible in special cases as in reactions from excited state surfaces where barriers are generally low in energy.

© 1982 Optical Society of America

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