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 double resonance quantum beat method has been demonstrated. Pyrimidine molecules were coherently excited into single rotational states of the S0 201 (13a1) vibrational level. The resulting hyperfine level coherences were then probed, after a variable time delay, by excitation to the S1 O0 level with subsequent fluorescence detection. Analysis showed that the quadrupole structure in the 201 (13a1) level is similar to that previously measured in the vibrational ground state. Applications of this method and possible experimental extensions are discussed.