The molecule displays internal rotation of the two non-equivalent methyl groups. The experimental data were reproduced quite well with the erham program. The present analysis and the data are based on
(1) L. Zou, J.-C. Guillemin, A. Belloche, J. K. Jørgensen, L. Margulès, R. A. Motiyenko, and P. Groner, 2023, Mon. Not. R. Astron. Soc. 520, 4089.
The calculation was provided by L. Zou. The present compilation contains many more low-J transitions compared with the published one. Itshould be sufficiently accurate for all observational purposes. Transitions with calculated uncertainties exceeding 0.1 MHz should be viewed with some caution.
Please note also that erham uses two σ values to label each symmetry component. This is incompatible with the VAMDC-CDMS requirements and does not agree with the convention of the classical CDMS to use one state number to label one symmetry species (or one vibrational state etc.). The following relations exist:
0 / 0 0 / A / AA,
1 / 0 1 / E1 / EA,
2 / 1 0 / E2 / AE,
3 / 1 1 / E3 / EE1,
4 / 1 2 / E4 / EE2.
No experimental lines have been merged in the present entry. The list of experimental lines can be accessed in the catalog archive.
Please note also that the partition function refers to the ground vibrational state.
The dipole moment components are from a quantum chemical calculation in (1).