Multiple ionisation and fragmentation of molecules

Siegmann B, Werner U, Lutz HO. Multiple ionisation and fragmentation of molecules. In: Australian Journal of Physics. Australian Journal of Physics. Vol 52. C S I R O PUBLISHING; 1999: 545-554

Ion-impact induced excitation and fragmentation of C60

Reinköster A, Siegmann B, Werner U, Lutz HO. Ion-impact induced excitation and fragmentation of C60. Radiation Physics and Chemistry. 2003;68(1-2):263-267.We studied the multiple ionization and fragmentation of C-60 in collisions with 50-300 keV H+, He+, Ne+, and 6.5-300 keV (.) z Ar2+ (z = 1-3) ions using a time- and position-sensitive multi-particle detector. Several aspects of C-2 evaporations, fullerene fission and multi-fragmentation processes are discussed. For Ar+ + C-60 the multi-fragmentation patterns depend on the projectile velocity and especially for slow ions strong variations occur. This behaviour is in accordance with recent non-adiabatic quantum molecular dynamic (NA-QMD) studies (Phys. Rev. Lett. 86 (2001) 5258). (C) 2003 Elsevier Science Ltd. All rights reserved

Complete Coulomb fragmentation of CO2 in collisions with 5.9 MeV u(-1) Xe18+ and Xe43+

Siegmann B, Werner U, Lutz HO, Mann R. Complete Coulomb fragmentation of CO2 in collisions with 5.9 MeV u(-1) Xe18+ and Xe43+. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS. 2002;35(17):3755-3765.We studied the ionization and fragmentation of CO2 in collisions with 5.9 MeV u(-1) Xe18+ and Xe43+ ions utilizing a position- and time-sensitive multiparticle detector. By coincident measurement of the momenta of correlated fragment ions the applied method yields a kinematically complete description of the fragmentation process. Of special interest are the 'Coulomb explosion' (CE) processes CO2 --> Cp+ + Oq+ + Or+ for which the released kinetic energy as well as angular correlations are determined. The measured angular spectra are-provided that the molecular vibrations Of CO2 are taken into account-in reasonable agreement with a simple CE model. This model is, however, insufficient to explain the observed energy distributions. Apparently the detailed electronic structure of them intermediate highly charged CO2 ion plays an important role

Multiple ionization and fragmentation of H2O in collisions with fast highly charged Xe ions

Siegmann B, Werner U, Lutz HO, Mann R. Multiple ionization and fragmentation of H2O in collisions with fast highly charged Xe ions. Journal of Physics B - Atomic Molecular and Optical Physics. 2001;34(18):L587-L593.The multiple ionization and fragmentation of H2O in collision with 5.9 MeV u(-1) Xe17+, Xe18+ and Xe43+ ions was studied using a position- and time-sensitive multiparticle detector which allows the coincident measurement of the momenta of correlated fragment ions. If all fragments from a particular fragmentation are detected, a kinematically complete study of the molecular break-up process is possible. For these Coulomb explosion processes the kinetic energy as wen as angular correlations are determined

Multi-fragmentation of C-60 after collisions with Arz+ ions

Reinköster A, Siegmann B, Werner U, Huber BA, Lutz HO. Multi-fragmentation of C-60 after collisions with Arz+ ions. Journal of Physics B - Atomic Molecular and Optical Physics. 2002;35(24):4989-4997.We studied the fragmentation Of C-60 molecules in collisions with slow Ar+ ions (v approximate to 0.04-0.55 au) and with Arz+ ions (z = 2, 3) at somewhat higher ions velocities (v approximate to 0.3-0.95 au). The measured mass spectra show C-60(q+) (q less than or equal to 5), smaller C-60-2m(q+) fullerenes and C-60-2m(q+). + C-n(+) fission products. Special attention is devoted to the C-60 multi-fragmentation process, i.e. the breakup.of the C-60 cage into several small C-n(+) fragments (n = 1-29). Up to seven correlated small Q fragments (n = 1-5) have been observed. The muld-fragmentation pattern depends on the projectile charge. Furthermore, it varies strongly with the projectile velocity for slow ions, whereas it becomes nearly constant for faster ions. This is in accordance with recent non-adiabatic quantum molecular dynamic calculations

Multiple ionization and fragmentation of CH4 in collisions with slow highly charged ions

Werner U, Siegmann B, Lebius H, Huber B, Lutz HO. Multiple ionization and fragmentation of CH4 in collisions with slow highly charged ions. In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. Nuclear Instruments & Methods in Physics Research Section B - Beam Interactions with Materials and Atoms. Vol 205. ELSEVIER SCIENCE BV; 2003: 639-642.The multiple ionization and fragmentation of methane was studied in collisions with slow highly charged Xe-ions utilizing a position- and time-sensitive multi-particle detector. The coincident measurement of the momenta of correlated fragment ions allows a detailed analysis of the fragmentation kinematics and the kinetic energy release can be derived for each break-up into charged fragments. Among the observed processes the spectra for H+ + CH3+ and H-2(-) + CH2-, showed the highest sensitivity to projectile characteristics. (C) 2003 Elsevier Science B.V. All rights reserved

Kinetic energy release distributions in the Coulomb explosion of N-2 molecules induced by fast, highly-charged-ion impact

Siegmann B, Werner U, Mann R, Kabachnik NM, Lutz HO. Kinetic energy release distributions in the Coulomb explosion of N-2 molecules induced by fast, highly-charged-ion impact. Physical Review A. 2000;62(2): 022718.The dissociation of molecular ions (N-2)(q+) produced by 4.7 MeV/amu Bi-57+,Bi-25+ and 5.9 MeV/amu Xe-43+,Xe-18+ ion impact on N-2 has been studied using the coincidence technique with a position- and time-sensitive multiparticle detector. The kinetic energy release distributions for all observed ion pairs Nq1+ +Nq2+ are measured. Analysis of the distributions is made with emphasis on the highly charged-molecular ions, q>3. In these cases the most probable total kinetic energy of the two fragments is quite well described by the Coulomb explosion model for point charges, while the measured width of the distributions is much larger than that predicted by this simplified model. We therefore suggest a more elaborate model of Coulomb fragmentation based on a statistical description of the individual potential energy curves of the molecular ion This enables us to describe both the position and the width of the kinetic energy release distributions. We suggest that the main cause of the large width of the distributions for the high q values is the spread of the potential energy curves at the equilibrium internuclear distance; this is mainly due to the dispersion interaction arising from the mutual polarization of the atomic ions

Kinetic Energy Release Distributions in the Fragmentation of O2 Molecules

Werner U, Siegmann B, Mann R, Kabachnik NM, Lutz HO. Kinetic Energy Release Distributions in the Fragmentation of O2 Molecules. Physica Scripta. 2001;T92(1):244-247-246.We report the first measurement of the kinetic energy release distributions of multiply charged oxygen ions produced in collisions of O-2 molecules with 5.9 MeV/amu Xe18+ and Xe43+ ions. The Slow Oq+ ions generated in the collision are detected in coincidence by a time- and position sensitive multiparticle detector. An analysis of correlated momenta of molecular fragments provides the kinetic energy release distribution for various reaction pairs O-2 --> O-q1+Oq2+ with a total charge up to q = q(1) + q(2) = 11. The position of the maximum and the width of the distributions are well described by the recently suggested Average Bunch Statistical (ABS) model

Orientation dependence of N-2 and O-2 multiple ionization in slow and fast collisions with highly charged Xe-ions

Siegmann B, Werner U, Lebius H, Huber B, Lutz HO, Mann R. Orientation dependence of N-2 and O-2 multiple ionization in slow and fast collisions with highly charged Xe-ions. In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. Nuclear Instruments & Methods in Physics Research Section B - Beam Interactions with Materials and Atoms. Vol 205. ELSEVIER SCIENCE BV; 2003: 629-633.The influence of the molecular orientation on the multiple ionization of N-2 and 02 was studied in collisions with highly charged Xe-ions at velocities of 0.2-0.3 and approximate to15 a.u. The applied technique is based on a position- and time-sensitive multi-particle detector which allows to determine the ionization cross-section as a function of the orientation of the molecular axis. At lower collision energies, e.g. in collisions with 360 keV Xe18+, no anisotropy was found, whereas in collisions with 770 MeV Xe18+ significant orientation effects appear at higher degrees of ionization. (C) 2003 Elsevier Science B.V. All rights reserved

Ion-impact induced multiple ionization and fragmentation of N2

Brinkmann U, Reinkoster A, Siegmann B, Werner U, Lutz HO, Mann R. Ion-impact induced multiple ionization and fragmentation of N2. In: Physica Scripta. Physica Scripta. Vol T80B. ROYAL SWEDISH ACAD SCIENCES; 1999: 171-172