The hyperfine structure in the rotational spectra of D 2 O: Lamb-dip measurements and quantum-chemical calculations

Thirteen rotational transitions of the doubly deuterated isotopic species of water, D2 16O, have been recorded in the millimeter- and submillimeter-wave region. The Lamb-dip technique has been used to resolve the hyperfine structure due to deuterium quadrupole coupling, due to spin–rotation as well as dipolar spin–spin interactions, thus enabling the determination of the corresponding hyperfine parameters to a good accuracy. The experimental investigation has been assisted by high-level quantum-chemical calculations of the hyperfine parameters.