No experimental data are available for this iosotopolog thus far. The spectroscopic were estimated as described in
(1) H. S. P. Müller, S. Thorwirth, and F. Lewen, 2020, J. Mol. Struct. 1207, Art. No. 127769.
The purely K-dependent parameters A, D_K, and an estimate of H_K, were taken from the main isotopic species as described in (1) based on ground state combination loops from
(2) H. S. P. Müller, P. Pracna, and V.-M. Horneman, 2002, J. Mol. Spectrosc. 216, 397.
An uncertainty of 30 kHz for B was propagated. This value should be roughly appropriate. Nevertheless, caution is advised for the entire entry.
At low temperatures, it may be necessary to discern between A-CH₃¹³C¹³CH and E-CH₃¹³C¹³CH. The A state levels are described by K = 3n, those of E state by K = 3n ± 1. The nuclear spin-weight ratio is 2 : 1 for A-CH₃¹³C¹³CH with K > 0 and all other states, respectively. The J_K = 1₁ level is the lowest E state level. It is 5.5847 cm^–1 above ground.
The dipole moment was assumed to agree with that of the main species from
(3) J. S. Muenter, and V. W. Laurie, 1966, J. Chem. Phys., 45, 855.