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Radiative Association of Ag and H: Formation of AgH from Ab Initio Calculations

Lin Jiang, Yu Wang, Yukun Yang, Xuanbing Qiu, Yali Tian, Guqing Guo, Ling Liu, Chuanliang Li, Yong Wu

Abstract

Radiative association processes leading to the formation of AgH in cold astrophysical environments are investigated for the first time using full quantum scattering theory. High accuracy potential energy curves and transition dipole moments for the low-lying electronic states (X$^1Σ^+$, A$^1Σ^+$, $1^1Π$, $3^1Σ^+$, $2^1Π$) are computed employing the internally contracted multireference configuration interaction method with Davidson correction. Vibrationally and rotationally resolved radiative association cross sections are calculated for transitions from these initial states to the ground X$^1Σ^+$ state. Prominent shape resonances arising from quasi-bound rovibrational levels behind centrifugal barriers are identified, with the $2^1Π\to$ X$^1Σ^+$ channel exhibiting the strongest contribution at low collision energies. Stimulated radiative association under blackbody radiation fields (up to $T = 20\,000$ K) produces modest enhancements, predominantly in the ground-state channel. Thermal rate coefficients computed over 10$^{-1}$--$10^4$~K reveal a general decreasing trend with temperature for all channels. The results provide essential kinetic data for astrochemical models of transition-metal hydride formation in low-temperature interstellar and circumstellar environments.

Radiative Association of Ag and H: Formation of AgH from Ab Initio Calculations

Abstract

Radiative association processes leading to the formation of AgH in cold astrophysical environments are investigated for the first time using full quantum scattering theory. High accuracy potential energy curves and transition dipole moments for the low-lying electronic states (X, A, , , ) are computed employing the internally contracted multireference configuration interaction method with Davidson correction. Vibrationally and rotationally resolved radiative association cross sections are calculated for transitions from these initial states to the ground X state. Prominent shape resonances arising from quasi-bound rovibrational levels behind centrifugal barriers are identified, with the X channel exhibiting the strongest contribution at low collision energies. Stimulated radiative association under blackbody radiation fields (up to K) produces modest enhancements, predominantly in the ground-state channel. Thermal rate coefficients computed over 10--~K reveal a general decreasing trend with temperature for all channels. The results provide essential kinetic data for astrochemical models of transition-metal hydride formation in low-temperature interstellar and circumstellar environments.

Paper Structure

This paper contains 10 sections, 8 equations, 6 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Method of calculation
  3. Electronic-structure methodology
  4. Radiative association cross sections and rate coefficients
  5. Results and Discussion
  6. Electronic structure of AgH
  7. Vibrationally and rotationally resolved cross sections
  8. Total cross sections and stimulated radiative association
  9. Thermal rate coefficients
  10. Conclusions

Figures (6)

  • Figure 1: Potential energy curves for the five low-lying $\Lambda-S$ states of AgH, transition dipole moments from excited states to X$^1\Sigma^+$, and permanent dipole moment of the X$^1\Sigma^+$ ground state.
  • Figure 2: Vibrationally and rotationally resolved radiative association cross sections at T = 0 K for the $\mathrm{X^1\Sigma^+ \to X^1\Sigma^+}$ channel in AgH. (a) Partial cross sections summed over vibrational quantum numbers $v$ for fixed rotational quantum numbers $J$ ($J=n$), compared to the total cross section; (b) Partial cross sections summed over $J$ for fixed $v$ ($v=n$); (c) Contributions from specific $(v, J)$ ro-vibrational states, with dominant resonances labeled.
  • Figure 3: Vibrationally and rotationally resolved radiative association cross sections for transitions from excited states to the ground state $\mathrm{X^1\Sigma^+}$ in AgH at $T=0$ K (spontaneous process).
  • Figure 4: Radiative association cross sections for transitions from the initial states X$^1\Sigma^+$, A$^1\Sigma^+$, $3^1\Sigma^+$, $1^1\Pi$, and $2^1\Pi$ to the ground state X$^1\Sigma^+$ in AgH, calculated at $T=0$ K.
  • Figure 5: Stimulated radiative association cross sections for AgH formation via transitions from the initial electronic states X$^1\Sigma^+$, A$^1\Sigma^+$, $3^1\Sigma^+$, $1^1\Pi$, and $2^1\Pi$ to the ground state X$^1\Sigma^+$ under blackbody radiation fields with temperatures of 0, 5000, 10000, 15000, and 20000 K.
  • ...and 1 more figures