title: Fragmentation of adenine under energy control.
abstract: We present results on the fragmentation of adenine dication as a function of the excitation energy. The adenine molecule is charged and excited in a single collision with Cl(+) ion at 3 keV and the excitation energy distribution is obtained for each fragmentation channel by measuring the kinetic energy loss of the projectile. This method named collision induced dissociation under energy control is based on the formation of a negative scattered projectile as a result of double electron capture from the target molecule. Comparison between the main dissociation channels of singly and doubly charged adenine shows that fragmentation patterns are very similar consisting mainly of the successive emission of neutral HCN or H(2)CN(+). The energy distributions of the parent adenine dication and the kinetic energy release of the fragments measured for the most abundant fragmentation channels confirms the assumption of successive emission dynamics. A specific fragmentation pathway of the adenine requiring less energy than the usual successive emission of neutral HCN could be identified. It consists of the emission of a charged H(2)CN(+) following on by the emission of a dimer of HCN (precisely HC(2)N(2)). This new channel, measured for a mean excitation energy of 8.4 eV for the adenine dication is very closed to the emission of HCN monomer measured at 7.9 eV. The implications of these results concern the formation of adenine in the sealed-tube reaction of HCN with liquid ammonia as well as the possible formation of the adenine molecule in the interstellar medium. This last point is briefly discussed in relation to astrobiology and exobiology interests.
authors.affiliation: Universite de Lyon, F-69622, Lyon, France. bredy@lasim.univ-lyon1.fr
authors.forename: Richard
authors.initials: R
authors.lastname: Brédy
authors.forename: Jéro Me
authors.initials: JM
authors.lastname: Bernard
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Guillaume
authors.initials: G
authors.lastname: Montagne
authors.forename: Bin
authors.initials: B
authors.lastname: Li
authors.forename: Serge
authors.initials: S
authors.lastname: Martin