The infrared signatures of polycyclic aromatic hydrocarbons ( PAHs ) are observed in a variety of astrophysical objects , including the circumnuclear medium of active galactic nuclei ( AGNs ) .
These are sources of highly energetic photons ( 0.2 to 10 keV ) , exposing the PAHs to a harsh environment .
In this work , we examined experimentally the photoionization and photostability of naphthalene ( C _ { 10 } H _ { 8 } ) , anthracene ( C _ { 14 } H _ { 10 } ) , 2-methyl-anthracene ( C _ { 14 } H _ { 9 } CH _ { 3 } ) and pyrene ( C _ { 16 } H _ { 10 } ) upon interaction with photons of 275 , 310 and 2500 eV .
The measurements were performed at the Brazilian Synchrotron Light Laboratory using time-of-flight mass-spectrometry ( TOF-MS ) .
We determined the absolute photoionization and photodissociation cross sections as a function of the incident photon energy ; the production rates of singly , doubly and triply charged ions ; and the molecular half-lives in regions surrounding AGNs .
Even considering moderate X-ray optical depth values ( \tau = 4.45 ) due to attenuation by the dusty torus , the half-lives are not long enough to account for PAH detection .
Our results suggest that a more sophisticated interplay between PAHs and dust grains should be present in order to circumvent molecular destruction .
We could not see any significant difference in the half-life values by increasing the size of the PAH carbon backbone , N _ { C } , from 10 to 16 .
However , we show that the multiple photoionization rates are significantly greater than the single ones , irrespective of the AGN source .
We suggest that an enrichment of multiply charged ions caused by X-rays can occur in AGNs .