Shubhadeep Biswas

Double differential distribution of electron emission in the ionization of water molecules by fast bare oxygen ions

The doubly differential distributions of low-energy electron emission in the ionization of water molecules under the impact of fast bare oxygen ions with energy of 48 MeV are measured. The measured data are compared with two quantum-mechanical models, i.e. the post and prior versions of the continuum distorted wave–eikonal initial state (CDW-EIS) approximation, and the first-order Born approximation with initial and final wavefunctions verifying correct boundary conditions (CB1). An overall excellent qualitative agreement is found between the data and the CDW-EIS models whereas the CB1 model showed substantial deviation. However, the detailed angular distributions display some discrepancies with both CDW-EIS models. The single differential and total cross-sections exhibit good agreement with the CDW-EIS models. The present detailed data set could also be used as an input for modeling highly charged ion induced radiation damage in living tissues, whose most abundant component is water. Similar measurements are also carried out for a projectile energy of 60 MeV. However, since the double differential cross-section data show similar results the details are not provided here, except for the total ionization cross-sections results.

Differential electron emission from multi-electronic targets under highly harged bare ion impact

We report a combined experimental and theoretical study of double differential electron emission in ionization of different multi-electronic atoms under fast highly charged bare ion impact. The main aim is to un-derstand the electron dynamics for these targets which is quite different from one or two electron systems.

Differential electron emission in the ionization of Ne and Xe atoms under fast bare carbon ion impact

Measurement of the energy and angular distributions of the double differential cross section (DDCS) of electron emission from Ne and Xe atoms in collision with 5 MeV u−1 bare carbon ions is reported. This study aimed to investigate the electron emission processes in the case of multi-electronic systems. In general, several clear differences between the electron emission spectra of Ne and Xe are found, which indicate the influence of the increasing number of electrons. For instance, the sharp peak due to the binary nature of collision is almost absent in the case of Xe, unlike Ne, which could be understood due to the increasing contribution from the strongly bound inner shell (such as ) electrons for the Xe atom. The forward–backward angular asymmetry has also been derived from the angular distributions. For Xe, the qualitative behaviour of the asymmetry parameter is seen to be quite different since it reveals structures due to Auger contributions. It is, in general, different and much lower than that for Ne, which shows the smooth behaviour that one finds for other lighter atoms like He. The single differential and total cross sections are also derived. The theoretical calculations based on the prior form of the continuum distorted wave-eikonal initial state (CDW-EIS) approximation have been provided for both the targets. Overall, it gives a very good agreement with the energy and the angular distributions of DDCS for Ne. For Xe, the agreement is not as good as for Ne. We also provide a detailed discussion on the DDCS obtained from different sub-shell ionization, estimated in this framework.

Author Correction: Differential electron emission from polycyclic aromatic hydrocarbon molecules under fast ion impact

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

Dressed projectile charge state dependence of differential electron emission from Ne atom

We study the projectile charge state dependence of doubly differential electron emission cross section (DDCS) in ionization of Ne under the impact of dressed and bare oxygen ions. Experimental DDCS results measured at different angles are compared with the calculations based on a CDW-EIS approximation using the GSZ model potential to describe projectile active-electron interaction. This prescription gives an overall very good agreement. In general a deviation from the q2-law was observed in the DDCS. The observations crudely identify the dominance of different projectile electron loss mechanisms at certain electron energy range.

Double differential electron emission in ionization of Coronene by fast ions

We present the absolute differential electron emission cross section of coronene under fast bare O-ion impact. The results show some features which cannot be explained by simple ion-atom type collision result. The difference of the energy and angular distribution data with that for CH4 and Ne may indirectly indicate the influence of collective excitation. We have performed the CB1 calculation for comparison.

Study of ion-atom ionization using dressed ions and effective projectiles charge state

In this report, we present a study of dressed ion projectile impact ionization of He and Ne atoms in the double differential cross section level. A large deviation from the q2-scaling of the DDCS was observed even for large impact parameter collisions. Different q-dependence (i.e. qn, n differs from 2) was found from which we calculated the effective projectile charge state. It also indicates the projectile screening mechanism which varies with impact parameter of the collision. For theoretical calculation we used GSZ model potential in the CDW-EIS framework, which gives an excellent agreement

Electron-DDCS Measurements of Water by C and Si Ion beams

Double differential distributions of electron emission from H2O target under the impact of C6+ and Si13+ ions with energy 4 MeV/u have been measured. The state-of-the art CDW-EIS model provided a good agreement with the data for C-ions whereas a substantial deviation is found for the Si ions. The derived single differential cross sections and total cross sections were also compared with different models.

Projectile q-dependence of electron DDCS in fast ion-He atom collision

We have measured the electron double differential cross section (DDCS) for 3.75MeV/u O8+ and O5+ colliding on He atom. The projectile q-dependence on electron emission for different angles is investigated. The DDCS ratios for two charge states are found to be dependent on emission angle and energy of the electrons. A good agreement is found between the experimental data of DDCS ratios and the continuum distorted wave-eikonal initial state (CDW-EIS) predictions.

Electron DDCS in ionization of H2O by 72 MeV O8+ ions: comparison with CDW-EIS post and prior forms

We have measured energy and angular distributions of double differential cross-sections (DDCS) for electron emission in ionization of water molecule under the impact of 72-MeV O8+ ions. The DDCS values have been compared with a state-of-the-art CDW-EIS calculation for both the prior and post forms of scattering matrix. The prior form of the CDW-EIS model produces better quantitative agreement with the experimental data.