Line Lists for the State of CS

Abstract

Rotation-vibrational line lists for eight isotopologues of carbon monosulphide (CS; 12C32S, 12C33S, 12C34S, 12C36S,13C32S, 13C33S,13C34S, and 13C36S) in their ground electronic state (X1Σ+) are calculated. An empirical potential function with the corrections of Born–Oppenheimer breakdown effects, which are determined by a direct potential fitting approach using over 4300 observed transition frequencies of 12C32S, 12C33S, 12C34S, and 13C32S, is used in line list calculations. The reproduced transition frequencies are within the observation uncertainties for the isotopologues with experimental data. The dipole moment functions are calculated using an ab initio method at a multireference configuration interaction method/cc-pv5z level with a large active space of electronic configuration. The dipole moment at equilibrium nuclear separation is almost identical to the experimental result. The calculated intensities agree excellently with the laboratory observations at 2573 K. The corresponding Einstein A coefficients and oscillator strengths are predicted. Partition functions for temperatures up to 7500 K have been calculated. The line lists can be used for spectroscopic measurements of CS in astronomical environments of various temperatures.

The 2020 release of the ExoMol database: Molecular line lists for exoplanet and other hot atmospheres

“…No change. We note that a line list for CS has also recently been supplied by Hou and Wei [196] and Xing et al [197] have extended consideration to rovibronic transitions for the lowest, A 1 -X 1 + , allowed electronic band.…”

Selection of the model functions for calculations of high-overtone intensities in the vibrational-rotational spectra of diatomic molecules

“…4 in [11]). In the study [11] a piecewise DMF with discontinuities of derivatives at r = 1 and 3.4 Å was proposed, but this should also lead to strong deviations from NIDL.…”

“…To calculate the intensities of dipole transitions, it is necessary to know the potential energy U(r) and the electric dipole moment d(r) of the molecule as functions of the internuclear distance r. In the case of transitions with a small change in the vibrational quantum number v, as a rule, v ≤ 2, the shape of these functions does not affect the result, but this is not the case for higher overtones. In particular, using the example of calculations of the intensities of transitions v ← 0 for SiO, CS, CO, and LiCl, it was shown that the use of non-analytical functions with discontinuous derivatives, for example, splines, leads to nonphysical saturation of the intensities at v ≥ 5 for SiO [10], v ≥ 7 for CS [1,11], CO and LiCl [10]. Therefore, in modern calculations, only analytic functions are used [12], but the problem still remains, since, as we will see, additional restrictions are needed.…”

Выбор Модельных Функций Для Расчёта Интенсивностей Высоких Обертонов В Колебательно-Вращательных Спектрах Двухатомных Молекул

“…3 в [1] и рис. 4 в [11]). В работе [11] была предложена кусочно-аналитическая ФДМ с разрывами производных при r = 1 и 3.4 ¦ , но это тоже должно приводить к сильным отклонениям от NIDL.…”

“…Для расчёта интенсивностей дипольных переходов необходимо знать потенциальную энергию U(r) и электрический дипольный момент d(r) молекулы как функции межъядерного расстояния r. В случае переходов с малым изменением колебательного квантового числа v, как правило, v ≤ 2, форма этих функций не влияет на результат, но для более высоких обертонов это не так. В частности, на примере расчётов интенсивностей переходов v ← 0 для SiO, СS, CO и LiCl было показано, что использование неаналитических функций, имеющих разрывы производных, например, сплайнов приводит к нефизическому насыщению интенсивностей при v ≥ 5 для SiO [10], v ≥ 7 для CS [1,11], CO и LiCl [10]. Поэтому в современных расчётах используют только аналитические функции [12], но проблема тем не менее остаётся, поскольку, как мы увидим, необходимы дополнительные ограничения.…”