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

Abstract

We study ionization and fragmentation of CO in electron loss and capture collisions of B 2+ , O 2+ , and Si 2+ ions at an energy of 71.4 keV/u (v = 1.69 a.u.). Coincidence measurements of fragment ions from CO and charge-selected ions were performed by means of a momentum three-dimensional imaging technique. Production cross sections of CO r+ and branching ratios into various fragmentation channels were obtained for r = 1-4. We also measured kinetic energy release (KER) in individual fragmentation channels. The KER spectra for r 2 are found to be different for electron loss and capture collisions, while the difference becomes small for r 3. As a measure of the degree of molecular fragmentation, the magnitude of the binding energy of the relevant electronic states seems the important parameter both in loss and capture collisions.

Kinetic-energy release inN2fragmentation by charge-changing collisions of2-MeVMizuno1, Yamada2, Tsuchida3 et al. 2010Phys. Rev. ASelf Cite7050View full textAdd to dashboardCite

“…In our recent study of CO fragmentation in charge-changing collisions of B 2+ , O 2+ , and Si 2+ ions [12], the fragmentation was found to differ strongly depending on the type of charge changing and on the projectile species. The former result means that the effective impact parameters are different in electron-loss and -capture collisions, leading to different energy deposition in these collisions.…”

“…In recent investigations three-dimensional momentum imaging techniques were used to determine molecular orientation [2][3][4][5][6] and kinetic-energy release (KER) during fragmentation [7][8][9][10][11][12][13]. As the molecular fragmentation occurs predominantly from a dissociative excited state, it is important to measure KER in individual fragmentation channels because it carries direct information about the initial dissociative excited states [8,14].…”

“…For fast heavy ions, however, b-resolved measurements have rarely been performed so far except those of cold target recoil-ion momentum spectroscopy [1] and those performed under projectile charge-changing conditions [6,[11][12][13][17][18][19][20][21]. In slow collisions of He 2+ and Ar 3+ with N 2 , Ehrich et al [11] found that KER spectra of two fragment N + ions are largely different for individual projectile final charge states.…”

“…The experimental method and apparatus are described elsewhere [6,12,17], so only a brief outline is given below. A beam of 2-MeV C + was carefully collimated ( 0.5 mm in diameter) and was incident on an effusive molecular beam target of N 2 .…”

“…Extraction of fragment ions into a TOF spectrometer was achieved over 4π sr for all fragment ions investigated. A total detection efficiency, given by the mesh-transmission rate (0.613) multiplied by the multichannel plate open area (0.57), was 0.35 [12]. The event-by-event recording was made with a digital storage oscilloscope (Wavepro7000, LeCroy), enabling us to measure flight times t and positions (x,y) of plural fragment ions produced in a single event.…”