Collisional excitation of HMgC3N by He: rate coefficients and astrophysical implications
Abstract
Reliable collisional data are essential for interpreting the rotational emission of HMgC3N under the non-equilibrium conditions of molecular clouds. We investigate the rotational excitation and de-excitation of HMgC3N induced by collisions with He, combining \textit{ab initio} calculations with quantum scattering theory. A two-dimensional potential energy surface (PES) for HMgC3N--He was constructed using the CCSD(T)-F12A method in conjunction with the aug-cc-pVTZ basis set. Quantum close-coupling (CC) calculation were then performed to obtain state-to-state integral cross sections and temperature-dependent rate coefficients for rotational transitions with Δj=±1, ±2, and ±3, covering rotational levels up to j=20 and temperatures from $3$ to $50$~K. The rate coefficients exhibit a clear propensity for Δj=±2 transitions. The resulting collisional data were incorporated into radiative transfer modelling to constrain the physical conditions and column density of HMgC3N from its observed spectral line emission. A χ2 minimization yields a best-fitting H2 volume density of n(H2)=1.233×105 cm−3 and column density of N(HMgC3N)=1.831×1012 cm−2. The derived column density is in approximate agreement with the observational estimate of (3.0±0.6)×1012 cm−2. These results provide new collisional data for non-LTE studies of HMgC3N and support a more realistic treatment of its rotational excitation and radiative transfer in molecular clouds.
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BibTeX
@misc{tian2026collisional,
title = {{Collisional excitation of HMgC$_3$N by He: rate coefficients and astrophysical implications}},
author = {Liman Tian and Ziyu Xiang and Wenli Zou and Xiaolin Chen},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.41876},
eprint = {2610.41876},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.41876},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Collisional excitation of HMgC_3N by He: rate coefficients and astrophysical implications
AU - Liman Tian
AU - Ziyu Xiang
AU - Wenli Zou
AU - Xiaolin Chen
PY - 2026
DA - 2026/10/30
PB - arXiv
DO - 10.48550/arxiv.2610.41876
UR - https://arxiv.org/abs/2610.41876
AB - Reliable collisional data are essential for interpreting the rotational emission of HMgC_3N under the non-equilibrium conditions of molecular clouds. We investigate the rotational excitation and de-excitation of HMgC_3N induced by collisions with He, combining \textit{ab initio} calculations with quantum scattering theory. A two-dimensional potential energy surface (PES) for HMgC_3N--He was constructed using the CCSD(T)-F12A method in conjunction with the aug-cc-pVTZ basis set. Quantum close-coupling (CC) calculation were then performed to obtain state-to-state integral cross sections and temperature-dependent rate coefficients for rotational transitions with Δj=±1, ±2, and ±3, covering rotational levels up to j=20 and temperatures from $3$ to $50$~K. The rate coefficients exhibit a clear propensity for Δj=±2 transitions. The resulting collisional data were incorporated into radiative transfer modelling to constrain the physical conditions and column density of HMgC_3N from its observed spectral line emission. A χ^2 minimization yields a best-fitting H_2 volume density of n(H_2)=1.233×10^5 cm^−3 and column density of N(HMgC_3N)=1.831×10^12 cm^−2. The derived column density is in approximate agreement with the observational estimate of (3.0±0.6)×10^12 cm^−2. These results provide new collisional data for non-LTE studies of HMgC_3N and support a more realistic treatment of its rotational excitation and radiative transfer in molecular clouds.
ER -