English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Galactic cosmic rays (CRs) play a crucial role in ionisation, dissociation,and excitation processes within dense cloud regions where UV radiation isabsorbed by dust grains and gas species. CRs regulate the abundance of ions andradicals, leading to the formation of more and more complex molecular species,and determine the charge distribution on dust grains. A quantitative analysisof these effects is essential for understanding the dynamical and chemicalevolution of star-forming regions. The CR-induced photon flux has a significantimpact on the evolution of the dense molecular medium in its gas and dustcomponents. This study is intended to evaluate the flux of UV photons generatedby CRs to calculate the photon-induced dissociation and ionisation rates of avast number of atomic and molecular species, as well as the integrated UVphoton flux. Our study takes advantage of recent developments in thedetermination of the spectra of secondary electrons, in the calculation ofstate-resolved excitation cross sections of H$_2$ by electron impact, and ofphotodissociation and photoionisation cross sections. We calculate the H$_2$level population of each rovibrational level of the $X$, $B$, $C$, $B'$, $D$,$B''$, $D'$ and $a$ states. We then compute the UV photon spectrum of H$_2$ inits line and continuum components between 72 and 700 nm, with unprecedentedaccuracy as a function of the CR spectrum incident on a molecular cloud, theH$_2$ column density, the isomeric H$_2$ composition, and the dust properties.The resulting photodissociation and photoionisation rates are, on average,smaller than previous determinations by a factor of about 2, with deviations upto a factor of 5. A special focus is given to the photoionisation rates ofH$_2$, HF, and H$_2$, as well as to the photodissociation of H$_2$, which wefind to be orders of magnitude higher than previous estimates.

Ultraviolet H$_2$ luminescence in molecular clouds induced by cosmic rays