Paper: astro-ph/0512561
Date: Thu, 22 Dec 2005 13:45:36 GMT (241kb)

Title: Photodissociation of organic molecules in star-forming regions II:
Acetic acid

Authors: S. Pilling (1 and 2), A. C. F. Santos (3) and H. M. Boechat-Roberty
(1) ((1) OV-UFRJ, (2) IQ-UFRJ, (3) IF-UFRJ)

Comments: Comments: 8 pages, 5 figures, 3 tables. Accepted to be printed in A&A
\\
Fragments from organic molecule dissociation (such as reactive ions and
radicals) can form interstellar complex molecules like amino acids. The goal of
this work is to experimentally study photoionization and photodissociation
processes of acetic acid (CH$_3$COOH), a glycine (NH$_2$CH$_2$COOH) precursor
molecule, by soft X-ray photons. The measurements were taken at the Brazilian
Synchrotron Light Laboratory (LNLS), employing soft X-ray photons from a
toroidal grating monochromator (TGM) beamline (100 - 310 eV). Mass spectra were
obtained using the photoelectron photoion coincidence (PEPICO) method. Kinetic
energy distribution and abundances for each ionic fragment have been obtained
from the analysis of the corresponding peak shapes in the mass spectra.
Absolute photoionization and photodissociation cross sections were also
determined. We have found, among the channels leading to ionization, that only
4-6% of CH$_3$COOH survive the strong ionization field. CH$_3$CO$^+$, COOH$^+$
and CH$_3^+$ ions are the main fragments, and the presence of the former may
indicate that the production-destruction process of acetic acid in hot
molecular cores (HMCs) could decrease the H$_2$O abundance since the net result
of this process converts H$_2$O into OH + H$^+$. The COOH$^+$ ion plays an
important role in ion-molecule reactions to form large biomolecules like
glycine.

\\ ( http://arXiv.org/abs/astro-ph/0512561 , 241kb)