Separation of enantiomers by ultraviolet laser pulses in H2POSH: pi pulsesversus adiabatic transitions

Different strategies to separate enantiomers from a racemate using analytic al laser pulses in the ultraviolet frequency domain are proposed for the pr ototype model system H2POSH. Wave-packet propagations on ab initio ground- and electronic-excited state potentials show that it is possible to produce 100% of enantiomeric excess in a sub-picosecond time scale using a sequenc e of pi and half-pi pulses. Alternatively, the previous transitions can be substituted by adiabatic counterparts, using chirped laser pulses and a hal f-STIRAP (stimulated Raman adiabatic passage) method which only transfers h alf of the population between appropriate levels. Such an overall adiabatic mechanism gains stability concerning the pulse areas and frequencies at th e expense of introducing new control variables, like the chirp and time del ay. (C) 2001 American Institute of Physics.