Rovibrationally resolved photodissociation of SH<sup>+</sup>

McMillan, Elizabeth; Shen, Guangmao; McCann, J. F.; McLaughlin, B. M.; Stancil, P. C.

doi:10.1088/0953-4075/49/8/084001

Cited by 20 publications

(12 citation statements)

References 39 publications

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“…In a similar manner to our recent all electron molecular structure and resulting dynamical studies on diatomic systems such as: SiO (Forrey et al 2016;Cairnie et al 2017), CS (Pattillo et al 2018;Forrey et al 2018), HeC + (Babb & McLaughlin 2017a), SH + (Shen et al 2015;McMillan et al 2016), CH + (Babb & McLaughlin 2017b), and HeAr + (Babb & McLaughlin 2018), the potential energy curves (PECs) and transition dipole moments (TDMs) for the eighteen singlet, triplet and quintet electronic states are calculated within an MRCI+Q approximation for the approach of ground state carbon atoms. That is, we use a state-averaged-multi-configuration-self-consistent-field (SA-MCSCF) approach, followed by multi-reference configuration interaction (MRCI) calculations together with the Davidson correction (MRCI+Q) (Helgaker et al 2000).…”

Section: Potential Curves and Transition Dipole Momentssupporting

confidence: 70%

Dicarbon Formation in Collisions of Two Carbon Atoms

Babb¹,

Smyth

McLaughlin

2019

ApJ

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Radiative association cross sections and rates are computed, using a quantum approach, for the formation of C 2 molecules (dicarbon) during the collision of two ground state C( 3 P) atoms. We find that transitions originating in the C 1 Π g , d 3 Π g , and 1 5 Π u states are the main contributors to the process. The results are compared and contrasted with previous results obtained from a semi-classical approximation. New ab initio potential curves and transition dipole moment functions have been obtained for the present work using the multi-reference configuration interaction approach with the Davidson correction (MRCI+Q) and aug-cc-pCV5Z basis sets, substantially increasing the available molecular data on dicarbon. Applications of the current computations to various astrophysical environments and laboratory studies are briefly discussed focusing on these rates.1 CO was also detected in the first overtone band (∆ν = 2). In SN 1987A individual rotational lines of CO and of SiO were detected at late epoch, see Abellán et al. (2017);Sarangi et al. (2018).

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Section: Potential Curves and Transition Dipole Momentssupporting

confidence: 70%

Dicarbon Formation in Collisions of Two Carbon Atoms

Babb¹,

Smyth

McLaughlin

2019

ApJ

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“…In Table 1 the equilibrium distance and dissociation energies, D e and D 0 , of SH + obtained in previous works are compared with the present results. All the theoretical values of D 0 (McMillan et al 2016;Stancil et al 2000;Song et al 2018;Zanchet et al 2013a) are within the experimental uncertainty (Huber & Herzberg 1979;Dunlavey et al 1979;Rostas et al 1984). Assuming that the accuracy of theoretical calculations improves with the size of the basis set, we conclude that the SH + diatomic considered in this work is slightly more accurate than the one used previously (Zanchet et al 2013a).…”

Section: Ab Initio Calculations and Analytical Fitsupporting

confidence: 67%

“…On the other hand, the constants of the H 2 diatomic are similar using the AVQZ or the AV6Z basis set, leading to the same D e . As a consequence, the increase of the SH + dissociation energy yields a reduction in the endothermicity of the reaction by about 5meV in our present PES, but this value may still be overestimated considering that McMillan et al (2016) find a D e that is 12 meV deeper using a aV6Z basis set in a study centered on the SH + diatomic. The second difference is not related to the size of the basis set, but to the sampling of ab initio points on the PES.…”

Section: Ab Initio Calculations and Analytical Fitmentioning

confidence: 55%

Formation of interstellar SH⁺from vibrationally excited H₂: Quantum study of S⁺+ H₂⇄ SH⁺+ H reaction and inelastic collision

Zanchet

Lique

Roncero

et al. 2019

A&A

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The rate constants for the formation, destruction, and collisional excitation of SH + are calculated from quantum mechanical approaches using two new SH + 2 potential energy surfaces (PESs) of 4 A and 2 A electronic symmetry. The PESs were developed to describe all adiabatic states correlating to the SH + ( 3 Σ − ) + H( 2 S ) channel. The formation of SH + through the S + + H 2 reaction is endothermic by ≈ 9860 K, and requires at least two vibrational quanta on the H 2 molecule to yield significant reactivity. Quasi-classical calculations of the total formation rate constant for H 2 (v = 2) are in very good agreement with the quantum results above 100K. Further quasi-classical calculations are then performed for v = 3, 4, and 5 to cover all vibrationally excited H 2 levels significantly populated in dense photodissociation regions (PDR). The new calculated formation and destruction rate constants are two to six times larger than the previous ones and have been introduced in the Meudon PDR code to simulate the physical and illuminating conditions in the Orion bar prototypical PDR. New astrochemical models based on the new molecular data produce four times larger SH + column densities, in agreement with those inferred from recent ALMA observations of the Orion bar.

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“…The direct photodissociation cross section of SH + is calculated ab initio by McMillan et al (2016) including transitions to several excited states. Their calculation from the v = 0 and J = 0 ground-state level was adopted here and added to this additional absorption into the longer-wavelength bound-levels of the A 3 Π state, which is known to predissociate for v ≥ 1 (Gustafsson et al 1988;Brites et al 2008).…”

Section: Sh + -Mercapto Ionmentioning

confidence: 99%

“…Their calculation from the v = 0 and J = 0 ground-state level was adopted here and added to this additional absorption into the longer-wavelength bound-levels of the A 3 Π state, which is known to predissociate for v ≥ 1 (Gustafsson et al 1988;Brites et al 2008). Oscillator strength of transitions into the vibrational levels of A 3 Π were calculated here using the potential-energy curves and transition dipole moments of McMillan et al (2016) and the methods of Sect. 4.3.49, but did not include details of their rotational structure.…”

Section: Sh + -Mercapto Ionmentioning

confidence: 99%

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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Rovibrationally resolved photodissociation of SH⁺

Cited by 20 publications

References 39 publications

Dicarbon Formation in Collisions of Two Carbon Atoms

Dicarbon Formation in Collisions of Two Carbon Atoms

Formation of interstellar SH⁺from vibrationally excited H₂: Quantum study of S⁺+ H₂⇄ SH⁺+ H reaction and inelastic collision

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

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Rovibrationally resolved photodissociation of SH+

Cited by 20 publications

References 39 publications

Dicarbon Formation in Collisions of Two Carbon Atoms

Dicarbon Formation in Collisions of Two Carbon Atoms

Formation of interstellar SH+from vibrationally excited H2: Quantum study of S++ H2⇄ SH++ H reaction and inelastic collision

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

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Rovibrationally resolved photodissociation of SH⁺

Formation of interstellar SH⁺from vibrationally excited H₂: Quantum study of S⁺+ H₂⇄ SH⁺+ H reaction and inelastic collision