Auger electron spectroscopy studies of CO on Ni spectral line shapes and quantitative aspects

The true secondary electron peak of aluminium is observed during the cleaning process controlled by Auger spectroscopy. The features which appear are studied in relation with the electron energy loss spectrum. This observation confirms the hypothesis of emission of secondary electrons by the plasmon decay.     

On the theory of linear absorption line shapes in gases

A detailed theory of the line shape in linear absorption spectroscopy of low-pressure gases is developed. The goal is to take into account all effects that come into play in the determination of Boltzmann's constant from measurements of the Doppler width. We demonstrate that there is no additional broadening from finite transit time across the laser beams. The molecular recoil and the second-order Doppler effect are included in the line shape thanks to a complete quantum treatment. The Mössbauer–Lamb–Dicke narrowing of Doppler lines by collisions is also included and the special cases of Galatry and Nelkin–Ghatak profiles are presented. To cite this article: C.J. Bordé, C. R. Physique 10 (2009).     

The shapes of Auger decay lines in photoelectron satellite spectra

The theory of the shapes of Auger decay lines of satellite two-hole-one particle states accompanying photoionization based on the Green's function method is developed. The lineshapes of Auger decay of satellite states [2 s 2 p ]( ^1,3 P )3 s ( ² P ), [2 s 2 p ]( ¹ P )4 s ( ² P ) and [3 s 3 p ]( ³ P )4 s ( ² P ) in valence p-photoelectron spectra of Ne and Ar atoms are calculated (hole states are indicated by square brackets throughout). It is shown that in some cases the Auger lineshapes reproduce the shape of the photoelectron satellite line, but in other cases Auger line may be narrower then the photoelectron line and may have opposite direction of asymmetry. The theoretical results are in agreement with experimental low-energy Auger spectra. Received: 25 May 1998 / Accepted: 2 October 1998     

Parametrizing the line shapes of near-threshold resonances

A parametrization is proposed for the line shapes of near-threshold resonances, which is based on the model of coupled channels and can include an arbitrary number of elastic and inelastic channels and bare poles. The proposed parametrization satisfies the requirements imposed by unitarity and analyticity, and is convenient for the data analysis embracing all available experimental information. The model parameters are physically meaningful, and their values can be found using different theoretical schemes.     

Approximate line shapes for hydrogen

Two independent methods are presented for calculating radiative transport within hydrogen lines. In Method 1, a simple equation is proposed for calculating the line shape. In Method 2, the line shape is assumed to be a dispersion profile and an equation is presented for calculating the half half-width. The results obtained for the line shapes and curves of growth by the two approximate methods are compared with similar results using the detailed line shapes by Vidal et al.     

Spectral line shapes. II

A spectral line shape function theory is extended for gaseous systems where reactive collisions can occur. The theory of subdynamics and the Fock-Tani representation are used in order to attempt this goal. The dependence of the spectral shape on the pressure and the reactive transition probability is clarified. Finally^a discussion concerning the above aspects and their possible applications has been included as well.     

Simple parameterization of dark-resonance line shapes

We have studied the dispersion and absorption line shapes of coherent population trapping resonances (dark resonances) in thermal cesium vapor. Outside the time-of-flight regime the line shapes can be described by a simple phenomenological model: a sum of a dispersive and an absorptive Lorentzian of identical width and position, whose relative weights depend on the detuning of the laser frequencies from the optical resonance. This functional form can be derived from a theoretical model for the full multilevel structure of an alkali atom. The analytical expressions for the parameters of the line shape model show the same behavior as the experimental data. Received: 4 October 2002 / Revised version: 30 October 2002 / Published online: 8 January 2003 RID="*" ID="*"Corresponding author. Fax: +41-26/300-9631, E-mail: robert.wynands@unifr.ch     

Excitonic line shapes of disordered solids

The optical absorption for a disordered one-dimensional excitonic solid has been studied by numerical methods. We have considered both Gaussian and binary energy fluctuations. Our results indicate that the physical properties associated with the spectra are selfaveraging. Results obtained on a single realization of random variables are consistent with recent ensemble averaged results obtained numerically on smaller samples. We also show that for binary disordered solids in the band splitting limit, spectra are dominated by cluster effects and can not be described through analytical treatments.     

Efficient computation of spectral line shapes

A method for computing spectral line shapes based on the Fourier representation of the Voigt profile is presented. The linearity of Fourier transforms is used to eliminate the need to evaluate the Voigt function repeatedly. Instead, the method requires computing only sines, cosines, and exponentials for each line and two Fourier transforms for the entire frequency range. The method is shown to be computationally more efficient than previous approaches for a wide variety of problems, particularly when there are many overlapping lines. In contrast to other approximations which have fixed error bounds, the accuracy of the transform method can be controlled by varying the frequency interval and number of points. A part of the R-band of molecular oxygen at 13,160 cm^-1 (7620Å) is computed to demonstrate the advantages of the transform method.     

Two-photon line shapes with near-resonant enhancement

We have studied a number of Doppler-free two-photon lines in Na₂ that are strongly enhanced by very nearly resonant intermediate states. Both experimentally and theoretically, it is found that the ratio of the height of the Doppler-free line to the Doppler-broadened background is a maximum when the offset of the enhancing level is about equal to the Doppler half-width.     

Influence of line interference on the vibration-rotation band shapes

The shapes of the CO, v₃, CO₂, and v₃ N₂O fundamental vibration-rotation bands have been studied at various temperatures and in the presence of several perturbing gases. Also the half-widths of CO vibration-rotation lines have been measured at 78 K. In the region of line wings, the measured absorption coefficients deviate from those given by the superposition of Lorentzian profiles. These deviations are explained by the collision-induced line interference that causes redistribution of absorption inside the band. A theory of line mixing is formulated which is based on Markov approximation and on the strong collision model. Simple analytical expressions are obtained for the band shape. The computed shapes are in satisfactory agreement with the experimental results. The deviations from the Lorentz absorption observed in pure CO and in CO-N₂ at low temperature are partially ascribed to the formation of van der Waals dimers.     

The line shapes of a tumbling triplet

The line shapes of a triplet spin system which interacts simultaneously with the molecular environment and with an externally applied field depend on the relative strengths of these interactions and on the motion of the molecule relative to the laboratory. In this paper line shapes are reported for zero, low, intermediate and strong applied fields, assuming that the molecular motion is due to strong collisions and that the tumbling rate is slow or intermediate.     

A kinetic theory of spectral line shapes

The methods of kinetic theory are used to describe the radiation from an atom immersed in a gas of perturbing particles. It is shown that the line shape can be expressed in terms of a one-particle distribution function. The appropriate BBGKY hierarchy of equations is derived. This hierarchy is then truncated by assuming that only two-body collisions are important. The resulting equations are solved to obtain a non-Markovian kinetic equation which describes the combined effects of Doppler and pressure broadening. When the Markovian assumption is applied, a generalized linear Boltzmann equation is obtained which describes the line shape in the region where the impact limit is valid and which also describes the phenomenon of collisional narrowing.This research was supported in part by the Advanced Research Projects Agency of the Department of Defense, monitored by Army Research Office-Durham under Contract No. DA-31-124-ARO-D-139.     

Recording of spectral line shapes in time

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 53, No. 1, pp. 90–94, July, 1990.     

Comparison of site-specific densities of states of Ga and As in cleaved and sputtered GaAs(110) by means of Auger line shapes

Site-specific densities of states for the Ga and As sites in GaAs(110) are derived from the M₁M_4,5V Auger lines and compared for the cleaved and sputtered surfaces. X-ray photoelectron spectroscopy, scanning electron microscopy, and LEED results for these surfaces are also presented. The results are interpreted in terms of a structure for the sputtered surface that consists of a two-phase mixture of Ga and disordered GaAs.     

Effects of individual line shapes on composite profiles and line series

We consider (i) the use of approximate ion microfield distributions as inputs into spectral line shapes and (ii) the effects of individual lines on unresolved transition array (UTA) profiles observed in highly ionized plasmas. Spectral line shapes and line wings have significant effects on mean opacity calculations.     

Giant Coster-Kronig transitions and intrinsic line shapes of the anomalous Pd M45VV Auger spectrum of Pd/Ag(100) dilute surface alloys

The Pd M4VV and M5VV Auger spectra of the 0.1 ML Pd/Ag(100) dilute surface alloy have been measured using Auger-photoelectron coincidence spectroscopy. The M4VV spectrum indicates that Pd 3d(3/2) core holes have a Coster-Kronig decay rate that is approximately 10 times that of Pd metal. Our calculations show that this giant enhancement arises from the local electronic structure of excited Pd atoms at the surface. Anomalous features in the Auger line shape are similar to those seen in dilute bulk PdAg alloys, and these features in the M5VV and M4VV lines are in good agreement with theoretical predictions.     

Auger line shape analysis of Zn3P2

The technique of Auger line shape analysis is applied to Zn₃P₂ single crystal. Zn₃P₂ is a semiconductor that has some potential as a material suitable for solar energy conversion. The measured line shapes are band-like and so are amenable to analysis and comparison with theory. The line shapes are recovered from the spectra by background subtraction followed by the Van Cittert deconvolution. This technique is first applied to the L₃VV line of copper and the results checked against those already in the literature. The line shapes for Zn₃P₂ are compared with band structure calculations. In general, there is good agreement between the theory and our measured valence band structure.