Rovibrational Line Lists of Triplet and Singlet Methylene

Area of Science:

• Chemical Physics
• Quantum Chemistry
• Spectroscopy

Background:

• Methylene (CH2) is a short-lived radical vital in interstellar hydrocarbon chemistry.
• Existing spectral line intensity data for CH2 is limited.
• CH2 plays a key role as an intermediate in complex hydrocarbon formation and destruction.

Purpose of the Study:

• To compute the first rovibrational line lists for both the ground triplet and first excited singlet electronic states of methylene (CH2).
• To provide accurate spectral data for CH2, essential for astrophysical and chemical studies.
• To enhance the understanding of CH2's role in interstellar chemical reactions.

Main Methods:

• Accurate ab initio potential energy surfaces (PES) were developed for both triplet and singlet CH2 states.
• High-level electronic structure calculations, including coupled cluster theory and basis set extrapolation, were employed.
• Ab initio dipole moment surfaces (DMS) were computed to determine transition probabilities.

Main Results:

• First comprehensive rovibrational line lists for triplet and singlet CH2 were generated.
• Accurate infrared band origins for singlet CH2 were achieved.
• Absorption spectra for both electronic states of methylene were predicted.

Conclusions:

• The generated line lists provide essential spectroscopic data for methylene (CH2).
• This work significantly advances the understanding of CH2's spectral properties and its role in interstellar chemistry.
• The accurate theoretical predictions pave the way for future observational validations.