Measurement Of Oscillator Strengths Research Articles

Measurement of relative transition oscillator strength via Rydberg six-wave mixing spectrum

Atomic-based field measurements have made significant progress in reproducibility, accuracy, and resolution enhancement. In this paper, the relative transition oscillator strength of excited 6P[Formula: see text] to nD[Formula: see text]/nD[Formula: see text] can be measured more accurately by spectral results of Rydberg six-wave mixing, meanwhile accompanying measured efficiency of Rydberg electromagnetically induced transparent and fluorescence is compared. Relative transition oscillator strength is obtained and demonstrated, it is observed that relative transition oscillator strengths are independent of primary quantum n in thermal vapor. The measured results are approached with theoretical calculation which can not only extend relative transition oscillator strength of the measurement way in an atomic system, but can also demonstrate six-wave mixing as nonlinear process read information of laser excite atoms more accurately.

Nd3+ doped [formula omitted] glass systems: Structural and optical properties

The structural and optical characteristic features of B2O3 + Li2O + CaO + CaF2 (BLCofNd) glasses incorporated with Nd3+ as a dopant of different concentrations (mol%) are reported. The X-ray diffraction technique was used to study structural characteristics such as the amorphous nature of BLCOFNd glass samples, Infrared spectroscopy was used to investigate the presence of functional groups and their impact on optical characteristics (FTIR), It reveals the creation of a network by borate and other components with the characteristics of glasses demonstrating different stretching and oscillating behavior of borate functional groups. The recorded UV Vis-NIR spectra of BLCofNd glasses reveal the prepared glasses have strong absorption at 584 nm in the visible region and 805 nm in the NIR region for the transitions 4I9/2→4G5/2 and 4I9/2→4F5/2, these transitions are due to the excitation of electrons by induced absorption. The density (gm/cc) measurements seem to be a rise in the values with a proportionality increase in CaO concentration (mol%), which directly relates to the decrease in the interionic distance (ri) making the glasses optically dense. Judd–Ofelt intensity parameters (Ω2, Ω4 and Ω6) highlights a covalency symmetry with a higher degree and surrounding lattice distribution of Nd3+ ions with other glass elements present in the network. The radiative properties of BLCOFNd glass samples mainly relate to parameters of radiative transition probability (AR), and corresponding branching ratios (βcal and βrad), which are derived from oscillator strength (fexp) measurements, FWHM or peak bandwidth (Δλp), stimulated emission cross-section and gain bandwidth (σse. Δλp) foresees that BLCofNd glasses are best candidates for laser host materials. The neodymium-doped borate glass exhibits a high peak power due to its emission at 1.049 μm wavelength and has its applications as lasing material and is prominently used as a source to produce the secondary waves in the measurement of pollutants in the atmosphere, optical amplifiers, and in the industry for their high intensity in emitted radiation.

Measurements of radiative lifetimes, branching fractions, transition probabilities, and oscillator strengths for Eu II and Eu III levels

Measurements of radiative lifetimes, branching fractions, transition probabilities, and oscillator strengths for Eu II and Eu III levels

Optical oscillator strengths of the valence-shell excitations of atoms and molecules determined by the dipole (γ,γ) method

The dipole (γ,γ) method, which is the inelastic X-ray scattering operated at a negligibly small momentum transfer, has been developed to determine the absolute optical oscillator strengths of the valence-shell excitations of atoms and molecules. This new method is free from the line saturation effect, and its Bethe-Born conversion factor varies much more slowly with the excitation energy than that of the dipole (e, e) method. Thus the dipole (γ,γ) method provides a reliable approach to obtain the benchmark optical oscillator strengths of the valence-shell excitations for gaseous atoms and molecules. In this paper, we give a review of the dipole (γ,γ) method and some recent measurements of absolute optical oscillator strengths of gaseous atoms and molecules.

Atomic Oscillator Strengths for Atmospheric Models

AbstractWe report new laboratory measurements of atomic oscillator strengths (log gfs) for stellar atmosphere models.

High-resolution oscillator strength measurements of the v' = 0,1 bands of the B −X, C −X, and E −X systems in five isotopologues of carbon monoxide

The photochemistry of CO and its isotoplogues affects the structure and evolution of many astronomical environments, including interstellar clouds, circumstellar disks around newly formed stars, and the envelopes surrounding highly evolved stars. When in the presence of a strong ultraviolet field, the primary destruction mechanism for interstellar and circumstellar CO is photodissociation, which is entirely governed by discrete line absorption into predissociating levels in the wavelength range 91.2 to 111.8 nm. Because the CO spectrum consists primarily of resolved line features, self-shielding effects in high-column density environments can lead to strong isotopic fractionation signatures in both CO and elemental oxygen and carbon; for example, CO self-shielding in the solar nebula has been invoked to explain the unusual oxygen isotope ratios observed in the earliest solar system condensates, viz. calcium-aluminum inclusions (CAIs) in primitive meteorites.

Hydrogen effect on nanostructural features of nanocrystalline silicon thin films deposited at 200 °C by PECVD

In this work, we reported hydrogen effect on nanostructural features of nanocrystalline silicon (nc-Si) thin films by using a plasma-enhanced chemical vapor deposition (PECVD) method at low deposition temperatures. Structural and optical properties have been investigated by means of X-ray diffraction, Raman scattering, photoluminescence (PL), and oscillator strength measurements. In addition, mechanical property was also investigated by stress measurements. It is shown that with an increase of the hydrogen content, R=[H2]/[SiH4], the crystalline volume fraction, the average crystallite size, <δ>, and the intensity of the 1.75–1.85eV PL band were increased, while the optical band-gap, Egopt, the peak energy and the intensity of the 2.15–2.25eV PL band were decreased. The oscillator strength and Egopt were increased when <δ> decreased. The remarkable result obtained from PL measurements showed that amorphous silicon (a-Si) exhibits a PL peak at 1.65eV and also possesses a wider band-gap than that of bulk Si. The stress in the nc-Si films is slightly compressive, which is favored for application of nc-Si to device technology. Moreover, addition of hydrogen-related molecules to the feed gases under low deposition temperature plays an important role, such as etching, cleaning, and coverage on the growing surface, in the crystallization of nc-Si.

Observational Constraints for Modeling Diffuse Molecular Clouds

AbstractGround-based and space-borne observations of diffuse molecular clouds suggest a number of areas where further improvements to modeling efforts is warranted. I will highlight those that have the widest applicability. The range in CO fractionation caused by selective isotope photodissociation, in particular the large 12C16O/13C16O ratios observed toward stars in Ophiuchus, is not reproduced well by current models. Our ongoing laboratory measurements of oscillator strengths and predissociation rates for Rydberg transitions in CO isotopologues may help clarify the situtation. The CH+ abundance continues to draw attention. Small scale structure seen toward ζ Per may provide additional constraints on the possible synthesis routes. The connection between results from optical transitions and those from radio and sub-millimeter wave transitions requires further effort. A study of OH+ and OH toward background stars reveals that these species favor different environments. This brings to focus the need to model each cloud along the line of sight separately, and to allow the physical conditions to vary within an individual cloud, in order to gain further insight into the chemistry. Now that an extensive set of data on molecular excitation is available, the models should seek to reproduce these data to place further constraints on the modeling results.

Measurements of Relative Transition Oscillator Strengths of Rydberg States in Cesium Magneto-Optical Trap

The oscillator strengths of 6 P 3/2 → n S / n D transitions are measured by fitting ultracold Cs Rydberg atom field-ionized spectra. The oscillator strength ratios η( n ) = f D 5/2 ( n )/ f D 3/2 ( n ) and ρ( n ) = f S 1/2 ( n + 2)/ f D 3/2 ( n ), which agree with the calculations based on the wave functions obtained by Numerov's method, are determined. The obtained results indicate that the ratios are almost independent of the principal quantum number n .

Laboratory measurements of oscillator strengths and their astrophysical applications1This review is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

We present an overview of current needs for accurate laboratory atomic transition probabilities (log(gf)) for astrophysical applications, particularly for iron group element spectra in the IR, optical, UV, and VUV spectral regions. Examples are given of our recent measurements, undertaken using the combination of high-resolution Fourier transform spectrometry and time-resolved laser-induced fluorescence. Laboratory measured log(gf) values are particularly important for the determination of elemental abundances in astrophysical objects. Advances in astronomical instrumentation, particularly access to underexplored regions (IR, vacuum UV,VUV), require improved accuracy and completeness of the atomic database for meaningful analyses of astrophysical spectra.

Oscillator strength measurements of atomic absorption lines from stellar spectra1This article is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.2Based in part on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de

Herein we develop a new method to determine oscillator strength values of atomic absorption lines with state-of-the-art detailed spectral synthesis calculations of the optical spectrum of the Sun and of standard spectral reference stars. We update the log(gf) values of 911 neutral lines observed in the KPNO–FTS flux spectrum of the Sun and high-resolution echelle spectra (R = 80 000) of Procyon (F5 IV–V) and [Formula: see text] Eri (K2 V) observed with large signal-to-noise (S/N) ratios of ∼2000 using the new Mercator–Hermes spectrograph at La Palma Observatory (Spain). We find for 483 Fe i, 85 Ni i, and 51 Si i absorption lines in the sample a systematic overestimation of the literature log(gf) values with central line depths below 15%. We employ a curve-of-growth analysis technique to test the accuracy of the new oscillator strength values and compare calculated equivalent line widths to the Moore, Minnaert, and Houtgast atlas of the Sun. The online SpectroWeb database at spectra.freeshell.org interactively displays the observed and synthetic spectra and provides the new log(gf) values together with important atomic line data. The graphical database is under development for stellar reference spectra of every spectral sub-class observed with large spectral resolution and S/N ratios.

Oscillator strength measurements of the 5s5p 3P 1 → 5s nd 3D 2 Rydberg transitions of cadmium

We report oscillator strengths distribution in the bound region of cadmium corresponding to the 5s5p 3P 1 → 5s nd 3D 2 (21 ≤ n ≤ 52) Rydberg transitions. The experiment was performed using two frequency doubled dye lasers simultaneously pumped by a common Nd:YAG laser in conjunction with an atomic beam set-up. The absolute photoionization cross section of the 5s5p 3P 1 intermediate state at the 5s 2S 1/2 ionization threshold has been measured as 20 (4) Mb using the saturation technique. The measured value of the photoionization cross section at threshold is used to extract the f-values of the above mentioned Rydberg transitions.

MEASUREMENTS OF THE RELATIVE OSCILLATOR STRENGTHS OF THE PRINCIPAL SERIES OF COPPER

New measurements of the relative oscillator strengths of copper for the 3 d 104 s 2 S 1/2→3 d 10n p 2 P 1/2, (7 ≤ n ≤ 13), and 2 P 3/2(7 ≤ n ≤ 23) series are reported. The data were acquired using the magneto-optical rotation spectroscopic technique, utilizing the linearly polarized light emitted by the 2.5 GeV electron accelerator, a 7 Tesla superconducting magnet, and a 3-meter high dispersion spectrograph with photographic detection. A quantum defect plot of the density of oscillator strengths of the discrete transitions is also presented.

Oscillator strength measurements of the highly excited 4s4p ^3P_1^o→4snd ^3D_2 transitions of zinc

We report experimentally determined oscillator strength distribution in the bound region of zinc corresponding to the 4s4p 3P1o→4snd 3D2 (23≤n≤55) transitions. The absolute photoionization cross section from the 4s4p 3P1o excited state at the 4s 2S1/2 ionization threshold has been determined as 54±8 Mbarns by using the saturated absorption technique. The measured value of the photoionization cross section at threshold is used to calibrate the oscillator strengths of the above-mentioned Rydberg transitions.

Radiative lifetimes of NO A Σ2+(v′=,1,2) and the electronic transition moment of the A Σ2+−X Π2 system

Improved measurements of the radiative lifetimes of NO A Σ2+(v′=0,1,2) are presented and used to update the absolute electronic transition moment for the NO γ bands. The pressure-dependent fluorescence decay rate was measured in a low-pressure, room-temperature, flow cell containing dilute mixtures of NO in N2 using time-resolved laser-induced fluorescence excited with a picosecond laser and detected with a microchannel-plate photomultiplier tube. Fluorescence decay rates were determined using an analysis procedure that accounted for the electronic response of the detection system and measurement noise. Radiative lifetimes were determined from an extrapolation of the measured decay rates to zero pressure. In comparison with prior measurements of these radiative lifetimes, the improved experimental approach and analysis procedure result in a significant improvement in the measurement precision. The accuracy of the fluorescence decay-rate measurements was confirmed by independent measurements using time-correlated single-photon counting and time-resolved probing of laser-excited population in A Σ2+ using 266 nm photoionization and charge detection. The measured radiative lifetimes are 192.6±0.2 ns for v′=0, 186.2±0.4 ns for v′=1, and 179.4±0.7 ns for v′=2. The measured lifetimes are shown to be in outstanding agreement with those predicted by an electronic transition moment that is identical in form to the function recommended by Luque and Crosley [J. Chem. Phys. 111, 7405 (1999)] after appropriate rescaling. This rescaling does not affect the agreement of the transition moment function with the previously reported vibrational branching ratios and improves agreement with previously reported absolute oscillator strength measurements. Based on the rescaled transition moment, updated values of absolute transition probabilities in the NO A Σ2+−X Π2 system are presented.

Fast-ion-beam laser-fluorescence measurements of oscillator strengths in the lanthanides

Atomic oscillator-strength data are of great interest to astronomers studying photospheric chemical abundances, stellar interiors and nucleosynthesis. We review the classic methods of measurement and then discuss our approach, which is based on fast-ion-beam laser-fluorescence techniques for both lifetime and branching-fraction measurements. Recently obtained large data sets in singly ionized lanthanides are discussed, with several examples illustrating the major advantages of this method: unambiguous identification of the upper level of a transition and greatly reduced spectral line blending.

Spectro web: oscillator strength measurements of atomic absorption lines in the sun and procyon

We update the online SpectroWeb database of spectral standard reference stars with 1178 oscillator strength values of atomic absorption lines observed in the optical spectrum of the Sun and Procyon (α CMi A). The updated line oscillator strengths are measured with best fits to the disk-integrated KPNO-FTS spectrum of the Sun observed between 4000 Å and 6800 Å using state-of-the-art detailed spectral synthesis calculations. A subset of 660 line oscillator strengths is validated with synthetic spectrum calculations of Procyon observed with ESO-UVES between 4700 Å and 6800 Å. The new log(gf)-values in SpectroWeb are improvements upon the values offered in the online Vienna Atomic Line Database (VALD). We find for neutral iron-group elements, such as Fe I, Ni I, Cr I, and Ti I, a statistically significant over-estimation of the VALD log((gf)-values for weak absorption lines with normalized central line depths below 15 %. For abundant lighter elements (e.g. Mg I and Ca I) this trend is statistically not significantly detectable, with the exception of Si I for which the log(gf)-values of 60 weak and medium-strong lines are substantially decreased to best fit the observed spectra. The newly measured log(gf)-values are available in the SpectroWeb database at http://spectra.freeshell.org, which interactively displays the observed and computed stellar spectra, together with corresponding atomic line data.

Oscillator strength measurements of the3p5(P1∕22)nd′[3∕2]2and[5∕2]2,3autoionizing resonances in argon

We present measurements of oscillator strengths of the $3{p}^{5}n{d}^{\ensuremath{'}}$ $J=2,3$ autoionizing Rydberg states in argon using two-step laser excitation in conjunction with an optogalvanic detection in a dc discharge cell. The $3{p}^{5}4{p}^{\ensuremath{'}}{[3∕2]}_{1,2}$ and ${[1∕2]}_{1}$ intermediate levels were populated via the $3{p}^{5}4s{[3∕2]}_{2}$ metastable state, collisionally populated in the discharge. The photoionization cross section from the $3{p}^{5}4{p}^{\ensuremath{'}}{[3∕2]}_{1,2}$ and ${[1∕2]}_{1}$ intermediate levels has been measured at the $3{p}^{5}\phantom{\rule{0.2em}{0ex}}^{2}P_{1∕2}$ ionization threshold as $34\ifmmode\pm\else\textpm\fi{}5$, $31\ifmmode\pm\else\textpm\fi{}5$, and $28\ifmmode\pm\else\textpm\fi{}4\phantom{\rule{0.3em}{0ex}}\mathrm{Mb}$, respectively, using the saturation technique. The measured absolute cross section values at the $3{p}^{5}\phantom{\rule{0.2em}{0ex}}^{2}P_{1∕2}$ threshold have been used to determine the $f$ values for the $4{p}^{\ensuremath{'}}{[3∕2]}_{1}\ensuremath{\rightarrow}n{d}^{\ensuremath{'}}{[5∕2]}_{2}$, $4{p}^{\ensuremath{'}}{[3∕2]}_{2}\ensuremath{\rightarrow}n{d}^{\ensuremath{'}}{[5∕2]}_{3}$, and $4{p}^{\ensuremath{'}}{[1∕2]}_{1}\ensuremath{\rightarrow}n{d}^{\ensuremath{'}}{[3∕2]}_{2}$ transitions. The extracted $f$ values are corrected by incorporating the contribution of the Fano line shape parameters for the autoionizing resonances.

Photoexcitation study of the 4s 2S1/2 state of atomic sodium

We report the first measurements of oscillator strengths for 4s 2S1/2 → np 2P1/2,3/2 (19 ⩽ n ⩽ 57) Rydberg transitions in atomic sodium using a thermionic diode ion detector in conjunction with an Nd:YAG pumped dye laser system. The f-values have been calibrated with the measured photoionization cross-section from the 4s 2S1/2 excited state at the first ionization threshold as 0.65(0.10) Mb. The binding energy of the 4s 2S1/2 level is determined as 15 709.444(8) cm−1 by employing the Rydberg relation to the observed np 2P1/2,3/2 Rydberg series. Addition of the binding energy to the known energy of the 4s 2S1/2 level yields the first ionization potential of sodium as 41 449.44(1) cm−1, which is in excellent agreement with the recognized value.

Fast-ion-beam laser-induced-fluorescence measurements of branching fractions and oscillator strengths in Nd II

We measured the spontaneous-emission branching fractions of 46 levels in Nd II, selectively populated via single-frequency laser excitation of a 10 keV ion beam. The levels studied had term energies up to 29 955 cm–1, and decay branches with spontaneous emission in the range 372–850 nm were detected. The experimental accuracy for branching fractions over 0.1 was ~7%. We used these branching fractions along with our previously determined radiative lifetimes to infer transition probabilities and oscillator strengths for 430 transitions, which are useful for stellar abundance determinations. PACS Nos.: 32.70Cs, 95.30Ky