Rovibrationally Resolved Photodissociation of AlH via Excited Electronic States

Qin, Zhaohui; Bai, Tianrui

doi:10.3847/1538-4357/ac06d1

“…A number of recent studies have considered the photodissociation of various molecules (Qin et al 2022(Qin et al , 2021, since the great improvement of computational capabilities facilitates highly accurate descriptions of molecular structure and dynamics. However, research into the photodissociation of MgH is very limited.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure, oscillator strength, and rovibrationally resolved photodissociation of ²⁴MgH

Deng,

Li,

Kun Yang

et al. 2024

A&A

0

View full text Add to dashboard Cite

A series of high-precision calculations for the electronic structure of MgH have been reported in the past two decades; however, most of them did not include the core-valence correlation and still exhibit distinct differences. Furthermore, the latest high-precision results have not been applied to the studies of photodissociation dynamics. The primary motivations of this paper are to calculate a more precise electronic structure of MgH considering a core-valence correlation and to provide the photodissociation cross-sections. The electronic structure of MgH is investigated by multi-reference configuration interaction calculations with Davidson correction (MRCI+Q). We performed two different sets of calculations to investigate the core-valence correlation and, as a result, obtained accurate potential energy curves (PECs) and transition dipole moments (TDMs). An extrapolation procedure was also employed to eliminate the error of basis set. Then, the photodissociation cross-sections were calculated using high-precision PECs and TDMs. The PECs and TDMs of the five lowest doublet electronic states, X$^2 B$'^2 E$^2 A$^2 and C$^2 are obtained from calculations including core-valence correlation, termed as CV-MRCI, while PECs of the ten lowest doublet states and three quartet states are also obtained from NCV-MRCI calculations without core-valence correlation. The spectroscopic constants and band oscillator strengths are also provided with high precision levels. The equilibrium $R_e$ and vertical excitation energy $T_e$ are only $0.1<!PCT!>$ different from the measurements. Based on the CV-MRCI results, the rovibrationally resolved photodissociation cross-sections for transitions from X$^2 to the other four states, as well as the total local thermodynamic equilibrium (LTE) cross-sections for temperatures up to 10000 K, are calculated.

show abstract

“…The theory and methodology of photodissociation for diatomic molecules and ions are well summarized in previous works (Kirby & Van Dishoeck 1989;Heays et al 2017;Hrodmarsson & van Dishoeck 2023). These computational methods are based on quantum mechanics and have been used to deal with the photodissociation processes of many diatomic molecules or ions, such as CS (Pattillo et al 2018), CN (El-Qadi & Stancil 2013) (Qin et al 2021a), AlCl (Qin et al 2021b), AlF (Qin et al 2022b), MgO (Bai et al 2021), MgH (Weck et al 2003), HCl and HF (Qin et al 2022a), etc. Recently, the ExoMol group have provided a new treatment for calculating photodissociation cross sections and rates (Pezzella et al 2021(Pezzella et al , 2022.…”

Section: Introductionmentioning

confidence: 99%

A Theoretical Study of Temperature-dependent Photodissociation Cross Sections and Rates for O₂

Qin,

Hu,

Bai

et al. 2023

ApJS

Self Cite

1

0

View full text Add to dashboard Cite

The photodissociation of O2 is thought to play a vital role in blocking UV radiation in the Earth’s atmosphere and likely has great importance in characterizing exoplanetary atmospheres. This work considers four photodissociation processes of O2 associated with its four electronic states, whose potential energy curves and transition dipole moments are calculated at the icMRCI+Q/aug-cc-pwCV5Z-DK level of theory. The quantum-mechanical approach is used to compute the state-resolved cross sections for two triplet transitions from the ground X 3 Σ g − state to the excited B 3 Σ u − and E 3 Σ u − states, and for two singlet transitions from the a 1Δg and b 1 Σ g + states to the 1 1Πu state, with a consideration of photon wavelengths from 500 Å to the relevant threshold. Assuming the populations of the initial states satisfy a Boltzmann distribution, the temperature-dependent photodissociation cross sections are estimated at gas dynamic temperatures of 0–10,000 K, in which the discrete progressions of the B 3 Σ u − ← X 3 Σ g − and E 3 Σ u − ← X 3 Σ g − transitions are also considered. The photodissociation rates of O2 in the interstellar, solar, and blackbody radiation fields are also calculated using the temperature-dependent cross sections. The resulting photodissociation cross sections and rates are important for the atmospheric chemistry of Earth and may be also useful for the atmospheric exploration of exoplanets.

show abstract

“…The ro-vibration spectra of the X 1 Σ + state of both AlH and AlD have been recorded and analysed by numerous groups, as well, using laser-diode and Fourier transform infrared methods, see Ito et al (1994), and White et al (1993) who measured a wide range of ro-vibrational lines of AlH, from v = 1 − 0 to v = 5 − 4, with high precision. Qin et al (2021) discussed the photodissociation of AlH, mainly for electronic bands 2 Ya. Pavlenko et al in the far UV.…”

Section: Introductionmentioning

confidence: 99%

AlH lines in the blue spectrum of Proxima Centauri

Pavlenko

¹

,

Tennyson

²

,

Yurchenko

³

et al. 2022

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

The recently computed ExoMol line lists for isotopologues of AlH are used to analyse the blue spectrum (4000–4500 Å) of Proxima Cen (M5.5 V). Comparison of the observed and computed spectra enables the identification of a large number of 27AlH lines of the A 1Π –X 1Σ+ band system: The spectral range covering 1-0, 0-0, and 1-1 bands are dominated by clearly resolved AlH lines. We reveal the diffuse nature of transitions close to the dissociation limit which appears in the form of increasingly wider (up to 5 Å) and shallower (up to the continuum confusion limit) AlH line profiles. The predicted wavelengths of AlH diffuse lines are systematically displaced. The effect of broadening by predissociation states on the line profiles is included by increasing the radiative damping rate by up to 5 orders of magnitude. We determine empirical values of damping rates for a number of the clean 0-0 Q-branch transitions by comparing the observed and synthetic stellar spectra. We find excellent agreement between our damping rates and lifetimes available in the literature. A comparison of 27Al1H ExoMol and REALH spectra shows that the observed spectrum is better described by the ExoMol line list. A search for 26Al1H lines in the Proxima Cen spectrum does not reveal any notable features; giving an upper limit of 27Al1H /26Al1H >100.

show abstract

Rovibrationally Resolved Photodissociation of AlH via Excited Electronic States

Cited by 12 publications

References 50 publications

Electronic structure, oscillator strength, and rovibrationally resolved photodissociation of ²⁴MgH

Electronic structure, oscillator strength, and rovibrationally resolved photodissociation of ²⁴MgH

A Theoretical Study of Temperature-dependent Photodissociation Cross Sections and Rates for O₂

AlH lines in the blue spectrum of Proxima Centauri

Contact Info

Product

Resources

About

Rovibrationally Resolved Photodissociation of AlH via Excited Electronic States

Cited by 12 publications

References 50 publications

Electronic structure, oscillator strength, and rovibrationally resolved photodissociation of 24MgH

Electronic structure, oscillator strength, and rovibrationally resolved photodissociation of 24MgH

A Theoretical Study of Temperature-dependent Photodissociation Cross Sections and Rates for O2

AlH lines in the blue spectrum of Proxima Centauri

Contact Info

Product

Resources

About

Electronic structure, oscillator strength, and rovibrationally resolved photodissociation of ²⁴MgH

Electronic structure, oscillator strength, and rovibrationally resolved photodissociation of ²⁴MgH

A Theoretical Study of Temperature-dependent Photodissociation Cross Sections and Rates for O₂