RAMAN CHIRPED ADIABATIC PASSAGE - A NEW METHOD FOR SELECTIVE EXCITATION OF HIGH VIBRATIONAL-STATES

It is demonstrated that efficient and high vibrational excitation can be achieved using non-resonant stimulated Raman transitions for subseq uent step by step climbing of vibrational levels. The pump laser (or b oth the pump and Stokes laser) frequency are to be swept in such a way that the frequency difference sweeping allows molecular anharmoniciti es of the final states to be matched. It is shown that amplitudes of s uccessive Raman transitions can be quantitatively described with the h elp of the effective Raman two-level systems. This selective scheme of vibrational excitation, called Raman chirped adiabatic passage (RCAP) , should be useful in controlling excited-state populations and chemic al reactions. The limitations of another well known adiabatic scheme o f population transfer, stimulated Raman adiabatic passage (STIRAP), ar e outlined and it is shown that RCAP is a complementary method to STIR AP. RCAP should be useful for selective excitation of highly polarizab le symmetric bonds such as metal-metal bonds. (C) 1997 by John Wiley & Sons, Ltd.