scholarly journals On the relationship between molecular spectroscopy and statistical mechanics: Calculation of vibrational-rotational energy levels and partition functions in the ground electronic state of BC2

2011 ◽  
Vol 76 (4) ◽  
pp. 557-573 ◽  
Author(s):  
Milan Sencanski ◽  
Ljiljana Stojanovic ◽  
Stanka Jerosimic ◽  
Jelena Radic-Peric ◽  
Miljenko Peric
Keyword(s):  
Energy Spectrum ◽  
Ab Initio Calculations ◽  
Electronic State ◽  
Molecular Spectroscopy ◽  
Energy Levels ◽  
Rotational Energy ◽  
Ground Electronic State ◽  
Partition Functions ◽  
Bending Vibrations ◽  
The Relationship

The results of extensive ab initio calculations of the vibrational- rotational energy spectrum in the ground electronic state of the BC2 molecule are presented. These data were employed to discuss the evaluation of the corresponding partition functions. Special attention was paid to the problems connected with the calculation of the partition functions for the bending vibrations and rotations about the axis corresponding to the smallest moment of inertia.

scholarly journals On the relationship between molecular spectroscopy and statistical mechanics: Calculation of partition functions for triatomic molecules undergoing large-amplitude bending vibrations

2011 ◽  
Vol 76 (4) ◽  
pp. 539-555 ◽  
Author(s):  
Milan Sencanski ◽  
Jelena Radic-Peric ◽  
Miljenko Peric
Keyword(s):  
Molecular Structure ◽  
Ab Initio Calculations ◽  
Structure Data ◽  
Large Amplitude ◽  
Molecular Spectroscopy ◽  
Energy Levels ◽  
Partition Functions ◽  
Bending Vibrations ◽  
Triatomic Molecules ◽  
The Relationship

The evaluation of partition functions for triatomic molecules undergoing large-amplitude bending vibrations is discussed. It was supposed that the needed molecular structure data were obtained by means of ab initio calculations. Special attention is paid to the coupling between the bending and stretching modes and the interplay between bending motions and rotations. An appropriate scheme for variational computation of the energy levels is developed.

scholarly journals ExoMol molecular line lists – XXXVII. Spectra of acetylene

2020 ◽  
Vol 493 (2) ◽  
pp. 1531-1545 ◽  
Author(s):  
Katy L Chubb ◽  
Jonathan Tennyson ◽  
Sergei N Yurchenko
Keyword(s):  
Angular Momentum ◽  
High Temperature ◽  
Electronic State ◽  
Energy Levels ◽  
Stellar Atmospheres ◽  
Ground Electronic State ◽  
Data Bases ◽  
Molecular Line ◽  
Line List ◽  
Maximum Value

ABSTRACT A new ro-vibrational line list for the ground electronic state of the main isotopologue of acetylene, 12C2H2, is computed as part of the ExoMol project. The aCeTY line list covers the transition wavenumbers up to 10 000 cm−1 (λ > 1 $\mu$m), with lower and upper energy levels up to 12 000 and 22 000 cm−1 considered, respectively. The calculations are performed up to a maximum value for the vibrational angular momentum, Kmax = Lmax  =  16, and maximum rotational angular momentum, J = 99. Higher values of J were not within the specified wavenumber window. The aCeTY line list is considered to be complete up to 2200 K, making it suitable for use in characterizing high-temperature exoplanet or cool stellar atmospheres. Einstein-A coefficients, which can directly be used to calculate intensities at a particular temperature, are computed for 4.3 billion (4 347 381 911) transitions between 5 million (5 160 803) energy levels. We make comparisons against other available data for 12C2H2, and demonstrate this to be the most complete line list available. The line list is available in electronic form from the online CDS and ExoMol data bases.

scholarly journals Six-dimensional potential energy surface and rotation-vibration energy levels of HNCO in the ground electronic state

2019 ◽  
Vol 84 (8) ◽  
pp. 845-859
Author(s):  
Mirjana Mladenovic
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Electronic State ◽  
Energy Surface ◽  
Energy Levels ◽  
Ground Electronic State ◽  
Vibration Energy ◽  
Projection Scheme ◽  
State Mixing

A six-dimensional potential energy surface based on CCSD(T)/cc--pCVQZ ab initio energy points was developed for HNCO in the 1A??ground electronic state and used to calculate rotation?vibration energy levels for J?5. The barrier to linearity was computed to be 1834 cm-1 for the angle HNC and 336 cm-1 for the angle NCO. The fundamental transitions were obtained for the main form and four isotopic variants of HNCO. The state mixing v3/2v6 was identified with the help of an adiabatic projection scheme.

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