Rotational spectrum of chloroform, "grass-roots among the forest of trees": The v2=1, v3=2, v5=1, and v6=3 vibrational states of CH35Cl3

We have recently analyzed the broadband millimeter-wave rotational spectrum of chloroform (CHCl3)-Cl-35 in the v(3) = v(6) = 1 (E symmetry) and v(6) = 2 (A(1) + E ) excited vibrational states . In the present work, we have used the same spectrum (recorded in the 150 -330 and 360-660 GHz spectral regions) for a rotational analysis of the v 2 = 1 and v(3) = 2 A(1) states of the same molecule, together with a new analysis of the v(5) = 1 (E) fundamental vibration. For the v(2) = 1 state (A(1), near 677 cm(-1)), the body of assigned data comprises 392 rotational transitions. The corresponding frequencies were fitted within an isolated-level model, with a standard deviation of 36.4 kHz, and the obtained parameters are in good agreement with the previous IR work. For the v(3) = 2 vibrational state (A(1) , near 734 cm(-1)), a total of 351 rotational transitions were assigned. Their fit was improved by inclusion of a second-order Coriolis coupling term with the v(5) = 1 fundamental level, providing standard deviation of 40.2 kHz. At the same time, the description of the v(5) = 1 vibration (E symmetry, 776 cm(-1)), studied previously with high-resolution as an isolated level, was also improved. The quantitative interpretation of the newly assigned 612 MMW data and the significantly extended set of IR assignments necessitated the introduction of the second-order Coriolis interaction with v(3) = 2, but more importantly of an anharmonic interaction with the v(6) = 3 (A(1) + A(2) + E, near 782 cm(-1)) level. For this latter level more than 200 rotational transitions, together with several series of rovibrational transitions, could finally be assigned and included in the fit. (c) 2021 Elsevier Ltd. All rights reserved.