atom and molecule photo cs (trac #386)

reported by: @CloudyLex

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

A.N. Heays, A. D. Bosman, E. F. van Dishoeck
(Submitted on 16 Jan 2017 (v1), last revised 19 Jan 2017 (this version, v2))

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.

Comments:   Corrected some inconsistent table/figure data. Significant change: Zn 
photoionisation rate corrected. Accepted for publication by A&A

Subjects:   Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies 
(astro-ph.GA)

Cite as:    arXiv:1701.04459 [astro-ph.SR]
    (or arXiv:1701.04459v2 [astro-ph.SR] for this version)

Migrated from https://www.nublado.org/ticket/386

{
    "status": "new",
    "changetime": "2019-02-04T13:02:49Z",
    "_ts": "1549285369825011",
    "description": "{{{\nPhotodissociation and photoionisation of atoms and molecules of astrophysical interest\n\nA.N. Heays, A. D. Bosman, E. F. van Dishoeck\n(Submitted on 16 Jan 2017 (v1), last revised 19 Jan 2017 (this version, v2))\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 new \nISRF rates generally agree within 30% with our previous compilations, with a few \nnotable exceptions. The reduction of rates in shielded regions was calculated as a \nfunction of dust, molecular and atomic hydrogen, atomic C, and self-shielding \ncolumn densities. The relative importance of shielding types depends on the species \nin question and the dust optical properties. The new data are publicly available from \nthe Leiden photodissociation and ionisation database. \n\nSensitivity of rates to variation of temperature and isotope, and cross section \nuncertainties, are tested. Tests were conducted with an interstellar-cloud chemical \nmodel, and find general agreement (within a factor of two) with the previous iteration \nof the Leiden database for the ISRF, and order-of-magnitude variations assuming \nvarious kinds of stellar radiation. The newly parameterised dust-shielding factors \nmakes a factor-of-two difference to many atomic and molecular abundances relative \nto parameters currently in the UDfA and KIDA astrochemical reaction databases. The \nnewly-calculated cosmic-ray induced photodissociation and ionisation rates differ \nfrom current standard values up to a factor of 5. Under high temperature and \ncosmic-ray-flux conditions the new rates alter the equilibrium abundances of \nabundant dark cloud abundances by up to a factor of two. The partial cross sections \nfor H2O and NH3 photodissociation forming OH, O, NH2 and NH are also evaluated \nand lead to radiation-field-dependent branching ratios.\n\nComments:\tCorrected some inconsistent table/figure data. Significant change: Zn \nphotoionisation rate corrected. Accepted for publication by A&A\n\nSubjects:\tSolar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies \n(astro-ph.GA)\n\nCite as:\tarXiv:1701.04459 [astro-ph.SR]\n \t(or arXiv:1701.04459v2 [astro-ph.SR] for this version)\n}}}",
    "reporter": "gary",
    "cc": "",
    "resolution": "",
    "time": "2017-03-29T13:37:02Z",
    "component": "atomic/molecular data base",
    "summary": "atom and molecule photo cs",
    "priority": "good to do",
    "keywords": "",
    "version": "trunk",
    "milestone": "no milestone",
    "owner": "nobody",
    "type": "enhancement"
}

cloudy-astrophysics / bug-tracker-migration-test

atom and molecule photo cs (trac #386) #388