Forbidden rotational Q branch of OPF3 observed by microwave Fourier transform spectroscopy

The Forbidden RotationalQ-Branch of CH3CF3: Torsional Properties and (A1−A2) Splittings

“…[9] is not necessary. The symmetrization of the basis breaks the Hamiltonian matrix in two blocks, one for A ϩ and one for A Ϫ , thereby increasing the efficiency of the computer calculations.…”

“…The (A 1 Ϫ A 2 ) splittings, of course, are determined primarily by ⑀Ј and hЈ 3 . An investigation of this type has been completed recently for OPF 3 (9). This molecule provides an excellent comparison standard for CH 3 CF 3 because the rotational spectra are virtually identical in form except that OPF 3 does not undergo internal rotation: A, (A Ϫ B), 0 , and D have similar values in the two molecules (3,6).…”

“…Thus CH 3 CF 3 provides a second test of the different reduction methods and redundancies for molecules with small (A Ϫ B) (15)(16)(17). This type of investigation is of greater interest now that effective values of the sextic distortion constants have been determined for a large number of symmetric tops (9,18).…”

“…The selection rules are ⌬J ϭ 0, Ϯ1; ⌬k ϭ Ϯ3; ⌬ ϭ 0. This method has been used to measure "forbidden" rotational energy differences in symmetric rotors without internal rotation, both for polar molecules such as PH 3 (7) and OPF 3 (8,9), and for non-polar systems such as BF 3 (10), PF 5 (11), and SO 3 (12). However, studies of internal rotation in symmetric rotors have not (to our knowledge) been previously published.…”

On the Rotational Analysis of the Ground Vibrational State of CH3D Molecule

“…In accordance with Refs. (16,17), the ambiguity in the effective rotational Hamiltonian leads to the following relations between the parameters of two models of Hamiltonian:…”