Determination of Stark Shifts and Widths Using Time Resolved Laser-Induced Breakdown Spectroscopy (LIBS) Measurements

Stark broadening parameters have been estimated for resonant lines of Al(I) using time resolved measurements. The relation between the various emission line characteristics at different phases of opacity have been utilized to obtain the value of plasma temperature and Stark width parameters from the experimental data. The observed value of the center line intensity and Lorentzian component of the line width are compared against a simulated value of these parameters for optically thin case. The plasma temperature and Stark broadening parameters are obtained for the best fit condition by matching the experimentally observed and the simulated values of intensity and line widths. The time resolved measurements result in much better estimates for Stark parameters by allowing multiple points for fitting keeping the number of variables limited. The Stark shift parameters are also obtained from the slope of the plot of observed central wavelength shifts versus observed electron number density which is measured as a function of time. Hence, a method utilizing multiple-time observation data to obtain the Stark broadening parameters for lines showing self-absorption has been demonstrated.

Quantitative estimation of elemental composition employing a synthetic generated spectrum

Composition of multielement samples is estimated by using a synthetic generated spectrum utilizing a nonlinear fitting routine. By fitting simultaneously a large number of emission lines, the error in the estimation is minimized. The procedure for synthetic spectrum generation includes self-absorption of emission lines by taking into account the number density of different species in the plasma. The Stark width of different emission lines is iteratively calculated based on the observed width and the degree of self-absorption in the individual lines. This procedure is found to be successful for achieving convergence of the retrieval algorithm even for dense spectra as well as for resolving merged lines with accuracy. This scheme was applied on a stainless steel and brass sample, and the laser-induced breakdown spectroscopy results match well with the reference value obtained from the electron probe microanalyzer measurement.

Three body dissociation of CS2(2+) subsequent to various S(2p) Auger transitions

Fragmentation kinematics of CS2 following various S(2p) Auger transitions is studied. Employing a combination of electron energy analysis and recoil ion momentum spectroscopy, changes in the dissociation channel yields, as well as the differences in the kinematical parameters for various bands of Auger hole states are presented. The fragmentation mechanism for dissociative channels leading to complete atomization of CS2(2+) molecular ion is studied in detail. We find that CS2(2+) does not retain linear geometry and is bent before undergoing concerted break-up. It is also observed that different geometric configurations of the CS2(2+) precursor result in different kinetic energy release values.

A combined electron-ion spectrometer for studying complete kinematics of molecular dissociation upon shell selective ionization

A combined electron-ion spectrometer has been built to study dissociation kinematics of molecular ions upon various electronic decay processes ensuing from ionization of neutral molecules. The apparatus can be used with various ionization agents. Ion time-of-flight (ToF) spectra arising from various electronic decay processes are acquired by triggering the ToF measurement in coincidence with energy analyzed electrons. The design and the performance of the spectrometer in a photoionization experiment is presented in detail. Electron spectra and ion time of flight spectra resulting from valence and 2p1∕2 ionization of Argon and those from valence ionization of CO are presented to demonstrate the capability of the instrument. The fragment ion spectra show remarkable differences (both kinematic and cross sectional) dependent on the energy of the ejected electron, corresponding to various electron loss and decay mechanisms in dissociative photoionization of molecules.

Observation of matter wave beat phenomena in the macrodomain for electrons moving along a magnetic field

We report here the observations that exhibit the existence of matter wave phenomena with wavelength in the macrodomain of a few centimeters, for electrons moving along a magnetic field from an electron gun to a collector plate situated behind a grounded grid. These are in accordance with the predictions of a quantumlike theory for charged particles in the classical macrodomain, given by one of the authors [R. K. Varma, Phys. Rev. A 31, 3951 (1985)] with a recent generalization [R. K. Varma, Phys. Rev. E 64, 036608 (2001)]. The beats correspond to two closely spaced "frequencies" in the system, with the beat frequency given, in accordance with the characteristics of a wave phenomena, by the difference between the two frequencies. The beats ride as a modulation over a discrete energy band structure obtained with only one frequency present. The frequency here corresponds to the distance between the electron gun and the detector plate as it characterizes the variation in the energy band structure as the electron energy is swept. The second "frequency" corresponds to the gun-grid distance. These observations of the beats of matter waves in this experiment, with characteristics in accordance with the wave algorithm, then establish unambiguously the existence of macroscopic matter waves for electrons propagating along a magnetic field.

A case report of esthesioneuroblastoma

Esthesioneuroblastoma (Olfactory Neuroblastoma) arises from the olfactory placode in the olfactory area of the nasal cavity. The age incidence ranges from 3 years to 79 years. It usually presents with nasal symptoms like obstructed nasal breathing and epistaxis. The diagnosis may be delayed for several months due to its slow growing nature. It may be misdiagnosed with other small round cell tumors. One such case is reported here due to its rare incidence, difficulty in early diagnosis and very aggressive behaviour compared to the reported series inspite of recommended treatment by different modalities.