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We have studied the electron emission from one of the polycyclic aromatic hydrocarbon (PAH) molecules namely, fluorene (C13H10), upon 3.5 MeV/u Si8+ ion impact. The experimentally measured absolute double differential cross sections (DDCS) are compared with the continuum distorted wave-eikonal initial state (CDW-EIS) model and the first Born approximation including correct boundary conditions (CB1). The measurements are carried out in the ejected e−-energy range of 1 eV–400 eV and in the angular range of 20°–160°. We have obtained the single differential and the total cross sections (TCSs) of e−-emission as well. The CB1 calculation largely underestimates the data. The CDW-EIS model, which is applied for the PAH molecule for the first time, provides an overall better agreement with the double differential, single differential and TCS data. The DDCS data for fluorene has also been compared with that for CH4 molecule, at a few angles. The forward–backward angular asymmetry shows a relatively flatter distribution compared to the theoretical predictions. The contribution due to the giant plasmon resonance could not be clearly observed except a mild indication in the asymmetry parameter. The angular distribution of the carbon KLL Auger electron cross section shows certain variations. The study of the KLL hyper-satellite component indicates the double K-ionization cross section is about 8.6% of the single K-ionization one. [ABSTRACT FROM AUTHOR]

The electronic absorption spectrum of diiodomethane in the 30 000-95 000 cm-1 region is investigated using synchrotron radiation, the spectrum in the 50 000-66 500 cm-1 region is reported for the first time. The absorption bands in the 30 000-50 000 cm-1 region are attributed to valence transitions, while the vacuum ultraviolet (VUV) spectrum (50 000-95 000 cm-1) is dominated by several Rydberg series converging to the first four ionization potentials of CH2I2 at 9.46, 9.76, 10.21, and 10.56 eV corresponding to the removal of an electron from the outermost 3b2, 2b1, 1a2 , and 4a1 non-bonding orbitals, respectively. Rydberg series of ns, np, and nd type converging to each of the four ionization potentials are assigned based on a quantum defect analysis. Time dependent density functional theory calculations of excited states support the analysis and help in interpretation of the Rydberg and valence nature of observed transitions. Density functional theory calculations of the neutral and ionic ground state geometries and vibrational frequencies are used to assign the observed vibronic structure. Vibronic features accompanying the Rydberg series are mainly due to excitation of the C-I symmetric stretch (v3) and CH2 wag (v8) modes, with smaller contributions from the C-H symmetric stretch (v1). UV absorption bands are assigned to low lying valence states 11B2, 11B1, 21A1, 31A1, 21B1, and 21B2 and the unusually high underlying intensity in parts of the VUV spectrum is attributed to valence states with high oscillator strength. This is the first report of a comprehensive Rydberg series and vibronic analysis of the VUV absorption spectrum of CH2I2 in the 50 000-85 000 cm-1 region. The VUV absorption spectrum of CD212 which serves to verify and consolidate spectral assignments is also reported here for the first time. [ABSTRACT FROM AUTHOR]

Gas mixing technique has been used in order to increase the current of highly charged ions of Xe at the TIFR‐ECRIA. The He, N2, O2, Ne, and Ar are used as support gases, and their effect on output currents of Xe ions is studied. The effective ion charge and the total loss rate of ions are calculated from the measured currents. It is found that molecular gases, such as N2 and O2, exhibit better mixing effect in the enhancement of output of highly charged Xe ions. Furthermore, we describe this 14.5‐GHz ECR ion source mounted on a high voltage (400 kV) deck, with its four beamlines, as well as the control system for the remote operation. [ABSTRACT FROM AUTHOR]

The experimental measurement of total electron transfer cross section in Bragg peak energy region is important to understand energy loss in the biomolecular system. In this study, we have measured state selective, K‐K electron capture and K‐ionization cross sections for adenine (C 5H 5N 5) in collisions with fast (2.5–5 MeV/u) C ions. These are compared with the data for smaller gas molecule, CO 2. These are derived from a study of the KLL‐Auger electron emission yields as a function projectile charge state. The K‐ionization cross‐section (σKI) data are compared with the ECUSAR (united and separated atom [USA] approximation with energy loss [E], Coulomb deflection [C], and relativistic [R] corrections) model calculation. The measured σKI data and the calculations are in good agreement. The K‐K transfer cross‐section (σK−K) data are compared with the CPSSR (perturbed stationary state [PSS] with Coulomb deflection [C] and relativistic corrections [R]) calculation that underestimates the measured data for such symmetric collision system. The energy dependence of σK−K for adenine is found to be flat in contrast to a sharp variation predicted by the model. The K‐transfer cross section is found to be substantial fraction of the K‐ionization. [ABSTRACT FROM AUTHOR]

Abstract: M X-ray yields of thin targets of 79Au and 83Bi in collisions with 50-300 keV protons have been measured. The production cross sections of Mζ[(M5-N3) + (M4-N2)], Mαβ[(M5-N6,7) + (M5-O3) + (M4-N6) + (M4-O2,3) + (M3-N2)], Mγ[(M3-N4,5) + (M2-N1)], Mm1[(M3-O1,4,5) + (M2-N4) + (M1-N2,3)] transitions and the total X-ray production cross-section are determined and compared to other available experimental values and also to those obtained from predictions of the PWBA and the ECPSSR models. The intensity ratios of the transitions are compared with the values calculated from the ECPSSR model. All existing experimental to theoretical ratios of the cross-sections as plotted as a function of the reduced velocity show a universal behaviour. Graphical abstract: [ABSTRACT FROM AUTHOR]