The torsion–rotation spectrum of perchloric acid, HClO4

摘要: Abstract The rotational spectrum of HClO4 has been observed in selected regions between 51.7 and 870 GHz. molecule is a near spherical rotor with moderately low barrier to internal rotation. characterized by strong μa, R-branch groupings B + C = 5276.78 MHz. Although there are no E torsional states, the R-branches show three distinct groups lines. There relatively tight cluster symmetric like transitions K = 3n, rather regular progression K = 3n + 2 high frequency less group K = 3n + 1 frequency. Because nearly spherical, energy as function K dominated dependent solutions Mathieu equation. This unusual level distribution gives rise numerous anomalous splittings shifts due avoided crossings within stacks well widely scattered μb transitions. fitting procedure will be described effective parameters presented. Rotational excited states at above top vt = 2–0 far infrared have assigned. dipole moment quadrupole coupling constants determined. Structural implications discussed.