NUCLEAR-QUADRUPOLE QUANTUM BEAT SPECTROSCOPY IN THE ELECTRONIC GROUND-STATE OF A POLYATOMIC MOLECULE BY AN IR-UV DOUBLE-RESONANCE METHOD

The feasibility of determining nuclear quadrupole hyperfine splittings in the ground electronic state of a polyatomic molecule using a doubl e resonance quantum beat method has been demonstrated. Pyrimidine mole cules were coherently excited into single rotational states of the S-0 20(1) (13a(1)) vibrational level. The resulting hyperfine level coher ences were then probed, after a variable time delay, by excitation to the S-1 0(0) level with subsequent fluorescence detection. Analysis sh owed that the quadrupole structure in the 20(1) (13a(1)) level is simi lar to that previously measured in the vibrational ground state. Appli cations of this method and possible experimental extensions are discus sed.