Photodissociation Processes in Diatomic Molecules of Astrophysical Interest

Kirby, K.; Dishoeck, E. F. van

doi:10.1016/s0065-2199(08)60097-4

Cited by 59 publications

(28 citation statements)

References 129 publications

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“…Quantum-chemical calculations of the excited electronic states of atoms and small molecules can be used to simulate photoabsorption, dissociation, and ionisation cross sections, and are particularly useful for species that are difficult to measure in the laboratory, such as radicals and ions (see Kirby & van Dishoeck 1988;van Dishoeck 1988;van Dishoeck & Visser 2015, for reviews).…”

Section: General Considerationsmentioning

confidence: 99%

“…Our database includes vertical-excitation cross sections computed for a number of molecules and summarised in van Dishoeck (1988), van Dishoeck et al (2006) and van Hemert & van Dishoeck (2008), based on our work and that of other groups (e.g., Kirby & van Dishoeck 1988;Roueff et al 2014). These results are based on high-level configuration interaction calculations (see van Dishoeck & Visser 2015, for a top level overview of such calculations).…”

Section: General Considerationsmentioning

confidence: 99%

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Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Heays

Bosman

Dishoeck

2017

A&A

442

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A new collection of photodissociation and photoionisation cross sections for 102 atoms and molecules of astrochemical interest has been assembled, along with a brief review of the basic physical processes involved. These have been used to calculate dissociation and ionisation rates, with uncertainties, in a standard ultraviolet interstellar radiation field (ISRF) and for other wavelength-dependent radiation fields, including cool stellar and solar radiation, Lyman-α dominated radiation, and a cosmic-ray induced ultraviolet flux. The new ISRF rates generally agree within 30% with our previous compilations, with a few notable exceptions. Comparison with other databases such as PHIDRATES is made. The reduction of rates in shielded regions was calculated as a function of dust, molecular and atomic hydrogen, atomic C, and self-shielding column densities. The relative importance of these shielding types depends on the atom or molecule in question and the assumed dust optical properties. All of the new data are publicly available from the Leiden photodissociation and ionisation database. Sensitivity of the calculated rates to variation of temperature and isotope, and uncertainties in measured or calculated cross sections, are tested and discussed. Tests were conducted on the new rates with an interstellar-cloud chemical model, and find general agreement (within a factor of two) in abundances obtained with the previous iteration of the Leiden database assuming an ISRF, and order-of-magnitude variations assuming various kinds of stellar radiation. The newly parameterised dust-shielding factors makes a factor-of-two difference to many atomic and molecular abundances relative to parameters currently in the UDfA and KIDA astrochemical reaction databases. The newly-calculated cosmic-ray induced photodissociation and ionisation rates differ from current standard values up to a factor of 5. Under high temperature and cosmic-ray-flux conditions the new rates alter the equilibrium abundances of abundant dark cloud abundances by up to a factor of two. The partial cross sections for H 2 O and NH 3 photodissociation forming OH, O, NH 2 and NH are also evaluated and lead to radiation-field-dependent branching ratios.

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Section: General Considerationsmentioning

confidence: 99%

Section: General Considerationsmentioning

confidence: 99%

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Heays

Bosman

Dishoeck

2017

A&A

442

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“…Then, the photodissociation cross section from initial rovibrational level v J can be expressed as [25] …”

Section: Photodissociation Approachmentioning

confidence: 99%

Rovibrationally resolved photodissociation of SH⁺

McMillan¹,

Shen²,

McCann³

et al. 2016

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. Photodissociation cross sections for the SH + radical are computed from all rovibrational (RV) levels of the ground electronic state X 3 Σ − for wavelengths from threshold to 500Å. The five electronic transitions,treated with a fully quantum-mechanical two-state model, i.e. no non-adiabatic coupling between excited states was included in our work.. The photodissociation calculations incorporate adiabatic potentials and transition dipole moment functions computed in the multireference configuration interaction approach along with the Davidson correction (MRCI+Q), but adjusted to match available experimental molecular data and asymptotic atomic limits. Local thermodynamic equilibrium (LTE) photodissociation cross sections were computed which assume a Boltzmann distribution of RV levels in the X 3 Σ − molecular state of the SH + cation. The LTE cross sections are presented for temperatures in the range 1000-10,000 K. Applications of the current photodissociation cross sections to interstellar gas, photon-dominated regions, and stellar atmospheres are briefly discussed.

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“…The state-to-state absorption cross section, σ n J (ν), which describes the molecular dissociation via Equation (3), is calculated using the following relation (Kirby & Van Dischoeck 1988):…”

Section: Dynamics Of Photodissociation Processesmentioning

confidence: 99%

PHOTON-INDUCED EVOLUTIONARY RATES OF LiHe⁺(¹Σ⁺) IN EARLY UNIVERSE FROM ACCURATE QUANTUM COMPUTATIONS

Bovino

Tacconi

Gianturco

2011

ApJ

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The radiative association rates for the formation of LiHe + molecules in their ground electronic state have been calculated employing an accurate ab initio potential energy curve and the dipole moment function. The enhancement of this rate, which may arise from stabilizing emissions stimulated by the cosmic background radiation field, has also been calculated and analyzed in the context of early universe conditions. Direct photodissociation processes have also been studied using local thermal equilibrium cross sections and rates are reported for temperatures between 600 and 9000 K. These photochemical processes are in turn analyzed and discussed as a function of the redshift z that is expected to operate in the early universe chemical kinetics. All data suggest very low residual abundances of this molecule and therefore its marginal role within early universe chemistry.

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Photodissociation Processes in Diatomic Molecules of Astrophysical Interest

Cited by 59 publications

References 129 publications

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Rovibrationally resolved photodissociation of SH⁺

PHOTON-INDUCED EVOLUTIONARY RATES OF LiHe⁺(¹Σ⁺) IN EARLY UNIVERSE FROM ACCURATE QUANTUM COMPUTATIONS

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Photodissociation Processes in Diatomic Molecules of Astrophysical Interest

Cited by 59 publications

References 129 publications

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Rovibrationally resolved photodissociation of SH+

PHOTON-INDUCED EVOLUTIONARY RATES OF LiHe+(1Σ+) IN EARLY UNIVERSE FROM ACCURATE QUANTUM COMPUTATIONS

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Rovibrationally resolved photodissociation of SH⁺

PHOTON-INDUCED EVOLUTIONARY RATES OF LiHe⁺(¹Σ⁺) IN EARLY UNIVERSE FROM ACCURATE QUANTUM COMPUTATIONS