Multiple-electron removal and molecular fragmentation of CO by fastF4+impact

Abstract

Multiple-electron removal from and molecular fragmentation of carbon monoxide molecules caused by collisions with 1-MeV/amu F + ions were studied using the coincidence time-of-Aight technique. In these collisions, multiple-electron removal of the target molecule is a dominant process. Cross sections for the different levels of ionization of the CO molecule during the collision were determined. The relative cross sections of ionization decrease with increasing number of electrons removed in a similar way as seen in atomic targets. This behavior is in agreement with a two-step mechanism, where erst the molecule is ionized by a Franck-Condon ionization and then the molecular ion dissociates. Most of the highly charged intermediate states of the molecule dissociate rapidly. Only CO+ and CO + molecular ions have been seen to survive long enough to be detected as molecular ions. The relative cross sections for the different breakup channels were evaluated for collisions in which the molecule broke into two charged fragments as mell as for collisions where only a single charged molecular ion or fragment were produced. The average charge state of each fragment resulting from CO~+~C'++0'+ breakup increases with the number of electrons removed from the molecule approximately following the relationship i = j=g/2 as long as K-shell electrons are not removed. This does not mean that the charge-state distribution is exactly symmetric, as, in general, removing electrons from the carbon fragment is slightly more likely than removing electrons from the oxygen due to the difference in binding energy. The cross sections for molecular breakup into a charged fragment and a neutral fragment drop rapidly with an increasing number of electrons removed.PACS number(s): 34.50.s, 35.80.+ s, 34.90.+ q

Measurement of kinetic energy release in CO fragmentation by charge-changing collisions of fast heavy ions

“…Note that a simple sum of the ionization potentials required for these ionized states shows 49.3 and 59.9 eV for (C 2+ , O + ) and (C + , O 2+ ), respectively. Table I also presents other experimental TOF data obtained by pulsed-beam coincidence methods in which individual charge-changing processes are not distinguished [1,11]. Their data of both production cross sections and branching ratios are in good agreement with each other irrespective of largely different incident species, velocities, and charges.…”

“…In the last few decades collision-induced molecular fragmentation was extensively studied for various combinations between projectile particles and molecules [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The investigation was carried out for the identification of fragment-ion pairs, kinetic energies of the fragments, and the orientation effect on the molecular fragmentation.…”

“…All values are given in %. Experimental data obtained by other groups[1,11] are also listed for comparison.…”

Electronic sputtering produced by fission fragments on condensed CO and CO2

“…The electron impact mass spectrum of CO gas shows a dominant CO ϩ peak, followed by three peaks of about the same intensity: C ϩ , O ϩ , and CO 2 ϩ [24]. The fragmentation of CO by 1 MeV/u F 4ϩ ions has CO ϩ as the main final product, followed by the C ϩ ϩ O 0 and C 0 ϩ O ϩ by channels with cross sections 6 to 7 times of magnitude lower [25], whereas 2.4 MeV/u Ar 14ϩ projectiles result in cross sections about 3 to 5 times lower [26]; C ϩ and C 2ϩ ion production is enhanced with respect to O ϩ and O 2ϩ , respectively. For CO 2 dissociation after collision with 3.6 MeV/u Si 8ϩ projectiles, it was reported that the peripheral O ions have larger kinetic energies than the central C ions [27].…”

Fragmentation ofCD+induced by intense ultrashort laser pulses

“…(4)], is usually the dominant dissociative ionization channel (see, e.g., the review by Codling and Frasinski [68] and Refs. [33,44,[69][70][71][72][73]). The latter, in contrast, has an asymmetric charge state distribution [CAD; see Eq.…”