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Updated: Jun 21, 2026
07:49
On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes
Published on: August 5, 2016
A variationally computed T = 300 K line list for NH3
Sergei N Yurchenko1, Robert J Barber, Andrey Yachmenev
1Institut für Physikalische Chemie und Elektrochemie, Technische Universität Dresden, D-01062 Dresden, Germany.
The Journal of Physical Chemistry. A
|July 29, 2009
Summary
Accurate ammonia rotation-vibration energy levels and intensities were calculated using advanced computational methods. This comprehensive ammonia line list reveals significant absorption features not present in current databases.
Area of Science:
- Quantum Chemistry
- Molecular Spectroscopy
- Computational Physics
Background:
- Accurate prediction of molecular spectra is crucial for atmospheric science and astrophysics.
- Previous calculations of ammonia (NH3) spectra had limitations in accuracy and completeness.
Purpose of the Study:
- To generate a comprehensive and accurate line list for ammonia (NH3).
- To improve the understanding of ammonia's rotation-vibration energy levels and transition intensities.
Main Methods:
- Utilized coupled cluster CCSD(T) calculations for the potential energy surface.
- Developed a new ab initio dipole moment surface at the frozen core CCSD(T)/aug-cc-pVQZ level.
- Employed the TROVE program for variational treatment of nuclear motion, incorporating algorithmic improvements.
Main Results:
- Calculated 3.25 million rotation-vibration transitions for (14)NH3 up to 12,000 cm(-1) and J=20.
- Achieved significant improvement in rotational energy level structure through geometry refinement.
- New line list shows good agreement with HITRAN but identifies missing absorptions.
Conclusions:
- The refined potential energy surface and new dipole moment surface lead to highly accurate ammonia spectra.
- The extensive ammonia line list provides a valuable resource for spectroscopic databases.
- Identified gaps in existing databases, particularly for near-infrared ammonia absorptions.
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