photo rates for molecules (trac #381)

reported by: @CloudyLex

Title:  
Photodissociation and photoionisation of atoms and molecules of astrophysical interest
Authors:    
Heays, A. N.; Bosman, A. D.; van Dishoeck, E. F.
Publication:    
eprint arXiv:1701.04459
Publication Date:   
01/2017
Origin: 
ARXIV
Keywords:   
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
Comment:    
Corrected some inconsistent table/figure data. Significant change: Zn photoionisation rate corrected. Accepted for publication by A&A
Bibliographic Code: 
2017arXiv170104459H
Abstract

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 processes involved. These have been used to calculate 
dissociation and ionisation rates, with uncertainties, in a standard ultraviolet 
interstellar radiation field (ISRF) and wavelength-dependent radiation fields. The 
new ISRF rates generally agree within 30% with our previous compilations, with a 
few notable exceptions. 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 shielding types depends 
on the species in question and the dust optical properties. The new data are 
publicly available from the Leiden photodissociation and ionisation database. 
Sensitivity of rates to variation of temperature and isotope, and cross section 
uncertainties, are tested. Tests were conducted with an interstellar-cloud 
chemical model, and find general agreement (within a factor of two) with the 
previous iteration of the Leiden database for the 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 H2O and NH3 photodissociation 
forming OH, O, NH2 and NH are also evaluated and lead to radiation-field-
dependent branching ratios.

Migrated from https://www.nublado.org/ticket/381

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    "status": "new",
    "changetime": "2019-02-04T13:02:49Z",
    "_ts": "1549285369825011",
    "description": "{{{\nTitle:\t\nPhotodissociation and photoionisation of atoms and molecules of astrophysical interest\nAuthors:\t\nHeays, A. N.; Bosman, A. D.; van Dishoeck, E. F.\nPublication:\t\neprint arXiv:1701.04459\nPublication Date:\t\n01/2017\nOrigin:\t\nARXIV\nKeywords:\t\nAstrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies\nComment:\t\nCorrected some inconsistent table/figure data. Significant change: Zn photoionisation rate corrected. Accepted for publication by A&A\nBibliographic Code:\t\n2017arXiv170104459H\nAbstract\n\nA new collection of photodissociation and photoionisation cross sections for 102 \natoms and molecules of astrochemical interest has been assembled, along with a \nbrief review of the basic processes involved. These have been used to calculate \ndissociation and ionisation rates, with uncertainties, in a standard ultraviolet \ninterstellar radiation field (ISRF) and wavelength-dependent radiation fields. The \nnew ISRF rates generally agree within 30% with our previous compilations, with a \nfew notable exceptions. The reduction of rates in shielded regions was calculated \nas a function of dust, molecular and atomic hydrogen, atomic C, and self-\nshielding column densities. The relative importance of shielding types depends \non the species in question and the dust optical properties. The new data are \npublicly available from the Leiden photodissociation and ionisation database. \nSensitivity of rates to variation of temperature and isotope, and cross section \nuncertainties, are tested. Tests were conducted with an interstellar-cloud \nchemical model, and find general agreement (within a factor of two) with the \nprevious iteration of the Leiden database for the ISRF, and order-of-magnitude \nvariations assuming various kinds of stellar radiation. The newly parameterised \ndust-shielding factors makes a factor-of-two difference to many atomic and \nmolecular abundances relative to parameters currently in the UDfA and KIDA \nastrochemical reaction databases. The newly-calculated cosmic-ray induced \nphotodissociation and ionisation rates differ from current standard values up to a \nfactor of 5. Under high temperature and cosmic-ray-flux conditions the new rates \nalter the equilibrium abundances of abundant dark cloud abundances by up to a \nfactor of two. The partial cross sections for H2O and NH3 photodissociation \nforming OH, O, NH2 and NH are also evaluated and lead to radiation-field-\ndependent branching ratios.\n\n}}}",
    "reporter": "gary",
    "cc": "",
    "resolution": "",
    "time": "2017-01-24T18:39:34Z",
    "component": "atomic/molecular data base",
    "summary": "photo rates for molecules",
    "priority": "good to do",
    "keywords": "",
    "version": "trunk",
    "milestone": "no milestone",
    "owner": "nobody",
    "type": "enhancement"
}

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photo rates for molecules (trac #381) #383