Electron emission in ionization of He and Ne by fast dressed oxygen ions and projectile-charge-state dependence

The double-differential cross sections (DDCS) of low-energy electrons emitted at forward, backward, and perpendicular directions are reported for collisions of 3.75 MeV/u Oq+ (q=5, 6, 7, 8) projectiles with He and Ne targets. The measured DDCS are found to be deviating from the q2 dependence throughout the entire energy region. The effect of projectile electrons, for the dressed ions, as a function of the impact parameter is clearly noticeable for large as well as low-impact parameter collisions. We also present a theoretical calculation based on the prior form of the continuum distorted wave-eikonal initial state approximation, in which the projectile-active electron interaction is modeled with the Green-Sellin-Zachor potential. This particular representation of the potential has been proven to give good qualitative results for projectiles with residual electrons. In addition to the total DDCS, the individual contributions from target ionization, projectile electron loss, and simultaneous ionization processes are also calculated. The total DDCS obtained from these calculations are shown to be in excellent agreement with the experimental observations.Fil: Biswas, Shubhadeep. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Kasthurirangan, S.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; España. Institute of Chemical Technology; IndiaFil: Misra, D.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Monti, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Fainstein, Pablo Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Tribedi, L.C.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; Españ

Electron emission from fluorene molecule in collisions with 3.5 MeV/u Si8+^{8+} ions

We present measured absolute double differential cross section (DDCS) of electron emission from fluorene (C13H10) molecule upon 3.5 MeV/u Si8+ ion impact. We have compared the energy and angular distributions of the DDCS with CB1 (Ist Born with correct boundary conditions) calculations. The e-DDCS shows an indication of collective excitation peak in low energy part of the spectrum at a few backward angles. The shape of the distribution has also been compared with that for a smaller molecule i.e. CH4

Ionization of uracil in collisions with fast bare ions

We study the atomic collisions with large molecules and simple atoms. The ionization and fragmentation spectra are investigated for uracil, a RNA base molecule, under the impact of fast bare C, O and F-ions. The experiments are conducted using a recoil-ion time-of-flight spectrometer. The energy dependence of the total ionization cross sections (TCS) and fragmentation yields are measured for MeV/u energies. In addition, the angular distribution of the electron double differential cross sections (DDCS) are also shown in some cases. The total cross sections of ionization and also the DDCS data are compared with the CDW-EIS calculations. The qualitative agreement is good but, in general, the theory tends to overestimate the data by a factor of 2.2. The angular distribution of electrons clearly indicates a good qualitative agreement except for the lowest energy electrons

Doubly differential distribution of electron emission in ionization of uracil in collisions with 3.5-MeV/u bare C ions

We report the energy and angular distribution of the electron emission from an RNA base molecule uracil in collisions with 3.5-MeV/u bare C ions. The absolute double differential cross sections (DDCS) are measured for emission energy between a few to 600 eV. The angular distributions are compared to those obtained for the O2 molecule in the same experiment. The single differential cross sections (SDCS) are also deduced. The energy and angular distributions of the DDCS and SDCS are compared with the state-of-the-art quantum-mechanical models based on continuum distorted wave-eikonal initial state (CDW-EIS) and correct boundary first Born (CB1) approximations which use a suitable molecular wave function for uracil. The models, however, give substantial deviations from the observed energy and angular distributions of the DDCS as well as SDCS. The CDW-EIS calculations are closer to the data compared to the CB1. In the case of uracil a large difference in the forward-backward emission of electrons was observed in comparison to that in collisions with an oxygen molecule

Study of

An implanted target (14N on Ta) is prepared and characterized via surface and bulk characterization processes. The depth profile of the implanted ions is obtained experimentally by populating a narrow resonance state of 15O through 14N(ρ,γ) reaction induced with a laboratory proton energy of 278 keV. The experimental profile is then compared with devoted simulations to under- stand the locations of the implantated ions in the lattice structure. Later, the lifetimes of a few excited states of 15O, relevant for applications in astrophys- ical scenario, have been determined using Doppler Shift Attenuation Method(DSAM)