Y. Iriki

Positive and negative cluster ions from liquid ethanol by fast ion bombardment

Secondary ion mass spectra have been measured for the first time for a liquid ethanol target bombarded by 2.0 MeV He(+) ions. Positive and negative ion spectra exhibit evidently a series of cluster ions of the forms [(EtOH)(n)H](+) and [(EtOH)(n)-H](-), respectively, in addition to light fragment ions from intact parent molecules. It was found that these cluster ions are produced only from liquid phase ethanol. Both positive and negative secondary ion spectra show similar cluster size distributions with almost the same decay slope. We also present for the first time the cluster ion distribution emitted from the liquid at different liquid temperatures.

Absolute doubly differential cross sections for ionization of adenine by 1.0-MeV protons

Double-differential ionization cross sections of adenine (C{sub 5}H{sub 5}N{sub 5}) by 1.0-MeV protons have been measured using a vapor-phase adenine target. Ejected electrons were analyzed by a 45 deg. parallel-plate electrostatic spectrometer in an electron energy range from 1 to 1000 eV at electron emission angles from 15 deg. to 165 deg. The effective target thickness of adenine was determined by a Rutherford forward scattering method and a vapor deposition method. Present data are in good agreement with recent calculations. Comparisons were made with other data on various hydrocarbon molecules. It was found that the ionization cross sections of these molecules can be scaled fairly well in terms of the total number of valence electrons.

Single-electron-capture cross-section scaling for low-q heavy ions at low energy

An attempt has been made to derive scaling laws for low-g heavy ions at low energy from our measured single-electron-capture cross-sections for single- and double-charged W, Ni, Fe, C, B, and Be ions.

Ionization induced by protons on isolated molecules of adenine: theory, modelling and experiment

We here report a comparison between semi-empirical and theoretical predictions in terms of differential and total cross sections for proton-induced ionization of isolated adenine molecules. Whereas the first ones are provided by existing analytical models, the second ones are based on two quantum-mechanical models recently developed within the 1st Born and the continuum distorted wave approximation, respectively. Besides, a large set of experimental data is also reported for comparisons. In all kinematical conditions here investigated, we have observed a very good agreement between theory and experiment whereas strong discrepancies were reported with the semi-empirical models in particular when doubly-differential cross sections are analysed.

Kinetic energy release in CO fragmentation by electron loss and capture collisions of fast B2+ ions

Ionization and fragmentation of CO molecules have been investigated in charge-changing collisions of B2+ ions at v = 1.69 a.u.. Fragment ions from CO were measured by using a momentum 3D imaging technique in coincidence with outgoing projectile charge states. We deduced the kinetic energy release (KER) associated with charge-changing collisions of B2+ to B3+, B1+ and B0+. The KER spectra in the fragmentation to C+ and O+ ions are found to be different to some extent for these loss and capture collisions. It is concluded that the electron loss collision populates the intact CO molecule to highly excited states of (CO)2+1 more effectively than electron capture collisions, resulting from different effective impact parameters associated with loss and capture collisions.

Ionization cross sections of gaseous amino acids of isoleucine by 2MeV He+ ions

Double differential cross sections for ionization by 2 MeV He+ ions have been measured for gaseous amino acids of isoleucine using a crossed beam method. Ejected electrons with energies below 600 eV were analyzed by a 45-degree electrostatic analyzer which was movable inside a collision chamber from 15 to 165 degrees with respect to the incident beam direction. K-LL Auger peaks of carbon, nitrogen, and oxygen were observed strongly with expected intensities from the number of consitituent atoms in an isoleucine molecule. Binary encounter peaks were also observed at angles smaller than 90 degrees.