Line Profile Indices Research Articles

Line-Profile Analysis of Excitation Spectroscopy in the Even 3p5(2P1/2)nl′[K′]J(l′=1,3) Autoionizing Resonances of Ar

The even-parity autoionizing resonance series 3p5np′[3/2]1,2, 3p5np′[1/2]1, and 3p5nf′[5/2]3 of Ar have been investigated exciting from the two metastable states 3p54s[3/2]2 and 3p54s′[1/2]0 in the photon energy range of 32500–35600 cm−1 with an experimental bandwidth of ∼0.1 cm−1. The excitation spectra of the even-parity autoionizing resonance series show typical asymmetric line shapes. New level energies, quantum defects, line profile index and resonance widths, resonance lifetime and reduced widths of the autoionizing resonances are derived by a Fano-type line-shape analysis. The line profile index q and the resonance widths Γ are shown to be approximately proportional to the effective principal quantum number n*. The line separation of the 3p5np′ autoionizing resonances is discussed.

Line-profile analysis of excitation spectroscopy in the even 4p5(2P1/2)nl′ [K′] J (l′ = 1,3) autoionizing resonances of Kr

The even-parity autoionizing resonance series 4p5 np′ [3/2]1,2, [1/2]1, and 4p5 nf′ [5/2]3 of krytpon have been investigated by laser excitation from the two metastable states 4p55s [3/2]2 and 4p55s′ [1/2]0 in the photon energy region of 29000–40000 cm−1 at experimental bandwidth of ∼0.1 cm−1. The excitation spectra of the even-parity autoionizing resonance series, most of which are experimentally studied for the first time in this work, show typical asymmetric line shapes. Complementary information on level energies, quantum defects, line profile indices and resonance widths, resonance lifetimes and reduced widths of the autoionizing resonances are derived by Fano-type line-shape analyses of the experimental results. Results from this work indicate that the line profile index (q) and the resonance width (Γ) are approximately proportional to the effective principal quantum number (n*); the line separation of the 4p5 np′ autoionizing resonances is also in good agreement with theoretical model.

Line-profile Analysis of Excitation Spectroscopy in Even 5p5(2P1/2)nl′ [K′]J (l′=1, 3) Autoionizing Resonances of Xe

The even-parity autoionizing resonance series 5p5np′ [3/2]1, [1/2]1, and 5p5nf′5/2]3 of xenon have been investigated, excited from the two metastable states 5p56s [3/2]2 and 5p56s′ [1/2]0 in the photon energy range of 28000–42000 cm−1 with experimental bandwidth of ̃0.1 cm−1. The excitation spectra of the even-parity autoionizing resonance series show typical asymmetric line shapes. New level energies, quantum defects, line profile indices and resonance widths, resonance lifetimes and reduced widths of the autoionizing resonances are derived by a Fano-type line-shape analysis. The line profile index and the resonance width are shown to be approximately proportional to the effective principal quantum number. The line separation of the 5p5np′ autoionizing resonances is discussed.

Study of the resonance structures of the interacting degenerate autoionizing Rydberg series perturbed by an interloper by multichannel quantum defect theory

A previous study by Lee et al (2011 J. Phys. B: At. Mol. Opt. Phys. 44 065002) on the resonance structures in autoionization Rydberg spectra, which are caused by two interacting autoionizing series perturbed by an interloper, is extended to the case of unequal coupling strengths. The method is applied to the Ba spectrum obtained by de Graaff et al (1990 Phys. Rev. A 42 5473–80). In this spectrum, the inter-series interaction term between two autoionizing Rydberg series perturbed by an interloper makes a negligible contribution to the spectral shape, even though its contribution to the cross section is found to be sizable. The peculiarity of the root structure of the line profile index for this spectra type could explain why q reversal frequently takes place around the resonance peak of an interloper and why the pattern of the satellite peaks leans towards the central peak.

Multichannel Quantum-Defect Study of q reversals in Overlapping Resonances in Systems involving 1 Open and 2 Closed Channels

This study examined the overlapping resonances in the systems involving 1 open and 2 closed channels using the phase-shifted version of multichannel quantum-defect theory (MQDT). The results showed that 21 patterns for the q reversals in the autoionization spectra are possible depending on the relative arrangements of the two simple poles and roots of the quadratic equations. Complete cases could be generated easily using the q zero planes determined using only 3 asymmetric spectral line profile indices. The transition of the spectra of the coarse interloper Rydberg series from the lines into a structured continuum by being dispersed onto the entire Rydberg series was found. The overall behavior of the time delays was found to be governed by the dense Rydberg series, which is quite different from the one of the autoionization cross sections that is governed by an interloper, indicating that different dynamics prevail for them. This is in contrast to the two channel system where both quantities behave similarly. The dynamics obtained in the presence of overlapping resonances is as follows. The absorption process is instant and dominated by a transition to the interloper line. This process is followed by rapid leakage into the dense Rydberg series, which has a longer residence time before ionization than that of the interloper state. This is because the orbiting period is proportional to <TEX>$\upsilon^3$</TEX> so that an excited electron has a shorter lifetime in the interloper state belonging to a lower member of the Rydberg series.

THE PHOTOMETRIC AND KINEMATIC STRUCTURE OF FACE-ON DISK GALAXIES. II. INTEGRATED LINE PROFILE CHARACTERIZATION AND THE ORIGIN OF LINE PROFILE ASYMMETRY

We perform a moments analysis of H I and H II global line profiles for 33 nearly face-on disk galaxies for the threefold purpose of rationalizing and interpreting line profile indices in the literature, presenting robust moment definitions with analytic error functions calibrated against Monte Carlo simulation, and probing the physical origin of line profile asymmetries. The first four profile moments serve as viable surrogates for the recession velocity, line width, asymmetry, and profile shape, respectively. The first three moments are superior, by a factor of ~2 in precision, to related quantities defined in the literature. First and third profile moments are related; skew can be used to calculate more accurate recession velocities from global profiles. Second and fourth profile moments are linked, corresponding to the known trend that narrow (but well resolved) line widths tend to be more Gaussian. Hα kurtosis also appears correlated with the spatially resolved line width of the ionized gas. No systematics appear between various measures of line width and true rotation speed other than the wide range of normalizations, which we calibrate. This conclusion and calibration, however, is highly sample dependent. The ratio of H II to H I widths is consistent with unity, even at low projected line width. There may be a trend toward a decrease in the ratio of H II to H I widths consistent with previous studies, but we also observe greater scatter. While there is good agreement between H I and H II first, second, and fourth moments, we find no positive correlation between skew measured from H I and H II profiles. Detailed analysis of the spatially resolved Hα distribution demonstrates that H II global profile asymmetries are dominated by differences in the gas distribution, not kinematic asymmetries.

Doubly excited resonances in the photoionization spectrum of Li+: experiment and theory

Absolute cross-section measurements for resonant double photoexcitation of Li+ ions followed by autoionization have been performed at high resolution in the photon energy range from 148 eV, just below the (2s2p, 2(0, 1)n+) resonance, to 198 eV (the region of the double ionization threshold). The measurements have been made using the photon–ion merged-beam endstation at the Advanced Light Source, Lawrence Berkeley National Laboratory, USA. The absolute cross-section measurements show excellent agreement with theoretical results from the R-matrix plus pseudo-state (RMPS) method. Comparisons between theory and experiment for the Auger resonance energies, autoionization linewidth (Γ) and the Fano line profile index q for several members of the principal (2snp, 2(0, 1)n+) and (3snp, 3(1, 1)n+) Rydberg series found in the photoionization spectra for the 1Po symmetry show satisfactory accord.

Photoexcitation of a dipole-forbidden resonance in helium.

We have observed photoexcitation of the dipole-forbidden 1s(2) 1S0-->2p(2) 1D2 resonance in helium by measuring the nondipolar forward-backward asymmetry of photoelectron angular distributions in the 2l2l(') autoionizing region. By exploiting the electric dipole-quadrupole interference in the excitation of both the 2s2p 1P1 and 2p(2) 1D2 levels, we have observed the quadrupole resonance in photoabsorption and extracted its Fano line shape parameters and the relative phase of the 1sEp and 1sEd continua. We find the quadrupole line profile index q(2) to be markedly different from theoretical expectations.

Identification of the Beutler-Fano formula in eigenphase shifts and eigentime delays near a resonance

Eigenphase shifts and eigentime delays near a resonance for a system of one discrete state and two continua are shown to be functionals of the Beutler- Fano formulas using appropriate dimensionless energy units and line profile indices. Parameters responsible for the avoided crossing of eigenphase shifts and eigentime delays are identified. Similarly, parameters responsible for the eigentime delays due to a frame change are identified. With the help of new parameters, an analogy with the spin model is pursued for the S matrix and time delay matrix. The time delay matrix is shown to comprise three terms, one due to resonance, one due to a avoided crossing interaction, and one due to a frame change. It is found that the squared sum of time delays due to the avoided crossing interaction and frame change is unity.

Photoionisation of neutral calcium

The R-matrix method as described by Burke and Taylor (1975) is applied to the photoionisation of neutral calcium from the 1Se ground state. Configuration-interaction wavefunctions are used to describe the initial Ca state and final Ca+ states. Total photoionisation cross sections are calculated for photon energies in the range 6.11 eV (2S threshold of Ca+) to 9.25 eV (2P threshold of Ca+) and are compared with the experimental measurements of Brown et al. (1973) and Connerade et al. (1980). A Cooper minimum is found just below the 2D threshold of Ca+ and its effect on the neighbouring series of Rydberg resonances is illustrated by a rapid change in the line profile indices, or q values, of these resonances as this minimum is crossed. LS coupling is used throughout.

Observation of Narrow Resonances in theH−Photodetachment Cross Section near then=3Threshold

Two pronounced dips in the ${\mathrm{H}}^{\ensuremath{-}}$ photodetachment cross section have been observed at photon energies of 12.650\ifmmode\pm\else\textpm\fi{}0.004 and 12.837\ifmmode\pm\else\textpm\fi{}0.004 eV, just below the hydrogenic $n=3$ threshold. These energies were reached by crossing a uv laser beam with a relativistic ${\mathrm{H}}^{\ensuremath{-}}$ beam. The dips are interpreted as the first two members of a $^{1}P$ Feshbach resonance series, of the + type, converging on $n=3$. Fano line shapes have been fitted to these structures to extract their intrinsic widths and line profile indices.

Line shape of a molecular resonance

In this paper we consider some implications of intramolecular electronic relaxation on the optical line shape of large molecules in the statistical limit. General expressions for the line shape were derived utilizing the Green's function formalism, which account both for interference with background absorption and for interference between resonances. The energy dependence of the line-width functions was elucidated. We have demonstrated that the line shape for an ‘isolated’ resonance is a fanian; however, as the line profile index is determined by the ratio of the level spacing to the non-radiative width, the corrections to the lorentzian line shape are small in this case. We have established the equivalence of the physical description utilizing a three-level crude adiabatic basis and a two-level adiabatic basis. In the case of overlapping resonances the line shape may be recast in terms of a modified Fano-type formula where the line profile index is energy dependent. The nature of interference effects in ...

A Discussion on photoelectron spectroscopy - The role of autoionization in molecular photoelectron spectra

The Fano-Mies theory of configuration interaction is applied to the photoionization of diatomic molecules, yielding an expression which gives the relative intensity of vibrational peaks in photoelectron spectra when one or more autoionizing states are in the vicinity of the excitation energy. In some cases the vibrational intensity distribution depends only on Franck-Condon factors connecting autoionizing and final states. Illustrative calculations for O2 show the transition from this limit to the limit of direct photoionization as the line profile index decreases.

Angle and Channel Dependence of Resonances ine-He Scattering near 60 eV

The ${\mathrm{He}}^{\ensuremath{-}}$ resonances at 57.1 and 58.2 eV in the electron scattering from He were studied as a function of angle in three inelastic channels corresponding to excitation of the $(1s2s)^{3}S$, $(1s2s)^{1}S$, and $(1s2p)^{1}P$ states of He. The line shapes of the resonances are found to vary with angle. The application of the Fano-Cooper formula, developed for the case of photon absorption, to resonances in inelastic electron scattering is discussed, along with a simple procedure for determining the line profile indices. The angular dependence of the $^{1}S$, $^{3}S$, and $^{1}P$ excitations at 56.5 eV was also measured out to about 60\ifmmode^\circ\else\textdegree\fi{}.