Electronic Transition Strengths Research Articles

Need a single-mode red laser, cheap? Check your pockets!

An inexpensive (<$5) key-chain model of red laser pointer (RLP) operates with typically 98% of its total emission in a single longitudinal cavity mode. The laser self-tunes with time, interpreted as due to thermal effects. The laser can also be tuned by varying its operating current and voltage. These properties permit one to quickly and easily record absorption spectral segments spanning ranges of 1–6cm−1, with high quantitative reliability, resolution, and accuracy. As examples, spectra of I2 are recorded in the 650nm region as a function of pressure for several RLP wavelengths and are used to estimate the strength of the underlying continuum (due to A←X absorption) with relative standard error less than 1%. Similarly, measurements of the integrated line absorption on selected lines in the B←X transition yield estimates of the electronic transition strength with unprecedented precision.

Optical excitations in small hydrogenated silicon clusters: comparison of theory and experiment

AbstractExcitation energies and absorption spectra of small hydrogenated silicon clusters are calculated within the framework of time‐dependent density‐functional response theory. The calculations employ several different approximations for the exchange‐correlation kernel, including the local density approximation as well as asymptotically correct Leeuwen–Baerends and Casida–Salahub potentials. The structures of the theoretical spectra are analyzed in detail and the positions of the absorption peaks obtained with different exchange‐correlation kernels are matched to the available experimental data based on the oscillator strength and symmetry of electronic transitions. The calculated absorption gaps are compared to the experimental values and discussed in terms of the applicability of common theoretical and experimental definitions for optical gaps to small clusters. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Application of molecular orbital calculations to interpret the chlorophyll spectral forms in pea photosystem II.

The energy and oscillator strength of electronic transitions of chlorophyll (Chl)-amino acid complexes were calculated by using molecular orbital methods. The energies varied widely with coordinated amino acids and the difference between the maximum and minimum energy was about 830 cm-1. This energy difference was comparable with the spreading of absorption bands for light-harvesting Chl-protein complexes of photosystem II (LHC II) of green plants. The feature of the Qy band for pea LHC II was interpreted with the aid of the calculated energies and oscillator strengths. Four spectral components of the band were assigned to individual Chl-amino acid complexes.

The electronic transition moment function for the Bu+(3Π)↔X 1Σg+ transition in I2

A new method is devised for extracting diatomic electronic transition strengths, as functions of internuclear distance R, from total radiative decay rates as a function of the vibrational level υ in the excited electronic state. The method involves least-squares inversion and utilizes an efficient and reliable sum rule for total radiative decay. When applied to the available data for the B–X transition in I2, the method indicates that the transition strength peaks at 1.85±0.1D2 near R=3.3 Å. This result is in qualitative agreement with most prior studies, from which, however, the level of quantitative consistency must be rated as poor.

Multi-Quantum-Well Effects on Electronic Structures and Optical Properties of GaP/AlP Superlattice

The electronic structure and optical transition strengths of the (GaP) m 1 (AlP) n 1 (GaP) m 2 (AlP) n 2 … type multi-quantum-well superlattices (MQS's) are calculated with use of the ab initio pseudopotential method within the local density approximation. It is shown that the thickest layers of GaP and AlP are a dominant factor of determining band-gap energy of MQS, while other thin “spacer” layers critically change the transition strengths. Especially, the strong transition strength is obtained when the spacer consists of thinner GaP and AlP layers. Excitonic effect on the photoluminescence is briefly discussed.

Band structures, optical transition strengths and their pressure dependence of (GaP) n(AlP) n short-period superlattices with n=3 to 10

The electronic structure and optical transition strengths of (GaP) n(AlP) n short-period superlattices with the clean (001) interface (SL(n,n)) are calculated for n=3 to 10 using the first principle pseudopotential method within the local density approximation (LDA). The calculated results show that SL(n,n) are pseudo-direct gap semiconductors for n=3 to 10. The calculated optical transition strengths for the pseudo-direct gap transitions oscillate between even and odd n-values and those for even n-values are as strong as those of direct-gap-semiconductors, though the transition strengths decrease gradually with increasing n. In order to investigate the character of the pseudo-direct gap, the hydrostatic pressure dependence of the pseudo-direct band-gap energy and of the optical transition strength for SL(4,4) is also calculated. The result predicts that the band-gap becomes smaller, i.e. the absorption edge exhibits a red shift, and the optical transition strength decrease gradually by applying pressure and thus that the conduction band state at the fundamental absorption edge is the X z state folded into Г.

The influence of the spatial structure on the electronic properties of porous silicon: quantum chemical study

In order to study the electronic properties of porous silicon (por-Si) we have investigated silicon nanoclusters with atomic configurations satisfying the general features of the radial and angular distribution functions of the por-Si structure modelled using the diffusion-limited aggregation model. The electronic structure calculations were performed within the intermediate neglect of differential overlap approximation of the Hartree-Fock-Roothaan scheme, while the restricted configuration interaction was employed in calculating excited states and transition rates. Both the electronic structure and optical transition strength are found to depend strongly on the cluster size and local environment. Importantly, the inclusion of many-electron effects is crucial in determining the transition rates. The low reactivity of some nanoclusters, together with their intermediate size and well-determined electronic properties, make them prospective initial blocks for the manufacturing of optoelectronic materials with desired characteristics.

Quantum Chemical Study of the Potential Energy Curves and Electronic Transition Strengths in HCl, XeCl, and HCl + Xe

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTQuantum Chemical Study of the Potential Energy Curves and Electronic Transition Strengths in HCl, XeCl, and HCl + XeGeorge F. Adams and Cary F. ChabalowskiCite this: J. Phys. Chem. 1994, 98, 23, 5878–5890Publication Date (Print):June 1, 1994Publication History Published online1 May 2002Published inissue 1 June 1994https://doi.org/10.1021/j100074a011RIGHTS & PERMISSIONSArticle Views214Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts

Intensities and electronic transition strengths of seven Te 2 visible and i.r. band systems

We present an experimental study of relative intensity distributions in the laser-flourescence spectra of the AO + u- XO + g, AO + u- X1 g, AO + u- b 1∑ + g, A1 - u- X1 - g, BO + u- XO + g, BO + u- X1 g, and BO + u- b 1∑ + g systems of the 130Te 2 molecule. Effective internuclear potentials have been determined by applying the RKR-procedure and accounting for rovibronic interaction. Franck-Condon factors and r-centroids have been calculated and tabulated. By combining expiremental results and calculations, we obtain the dependence of the electronic transition strength on internuclear distance in the r-centroid approximation. Normalization over the lifetimes of the rovibronic levels of the excited electronic states enabled us to determined absolute values of the electronic transition strengths with proper account for branching coefficients of the lower electronic terms.

Determination of electronic transition strengths in diatomic molecules using laser-induced fluorescence: Application to 80Se 2BOu+- XOg+ and B1 u+- X1 g+

A semiempirical approach for determining the dependence of the strength of an electronic transition S e ( R) on internuclear distance in the R-centroid approximation has been analyzed. This approach uses experimental data on relative intensities of resonance series from laser-induced fluorescence, as well as on lifetimes of separate rovibronic levels ( v′, J′) of the excited electronic state. Using BO u +- XO g + and B1 u +- X1 g + systems of the 80Se 2 molecule as an example, the possibility of applying the adiabatic and R-centroid approximation is discussed. The effect of Franck-Condon factor errors on S e ( R) values is considered, accounting also for errors due to imperfection of the set of molecular constants used. Experimentally measured relative intensities of three resonance series are presented for the above-mentioned systems with fixed upper levels ( v′, J′), obtained by 4880, 4965, and 5145 Å Ar +-laser excitation. These have been used to determine dependences of the electronic transition strength on the R-centroid. Using the kinetics of fluorescence decay, lifetimes of upper levels τ v′ J′ have been determined and further used to obtain absolute values of S e ( R).

Intensities of the laser-induced fluorescence of 130Te 2 and electronic transition strengths for the AO u+- XO g+ and BO u+- XO g+ systems

The intensities of the laser-induced fluorescence spectra of 130Te 2, excited by Ar + and He-Cd + lasers, are measured for the AO u +- XO g + and BO u +- XO g + systems. The RKR potentials of the A, B and X states are calculated. These potentials are used for calculating Franck-Condon factors and r-centroids with due respect to rotation. The relative r-centroid dependences of the electronic transition strength were obtained first and then normalized in lifetimes.

Electronic Transition Strengths for Diatomic Molecules

Abstract The normalized dependences of electronic transition strengths on the internuclear distance Se(R) are recommended in the review for 128 band systems of diatomic molecules. Se values, obtained under an assumption of Se(R) = const, are recommended for 98 systems. The recommendations were made after the data published till 1986. The works on experimental determination and ab initio calculations of the electronic transition strengths Se(R) and moments D(R), of the band fvτ and electronic fe oscillator strengths, of the radiative lifetimes τ have been considered. The re-commendation has been made according to the general scheme based on the principles discussed in the paper.

A study of variation of electronic transition moment of the B-X system of I2from its laser-excited fluorescence spectrum

Fluorescence in the B 3 Pi (0+u)-X 1 Sigma g+ system of I2 excited with 5145 AA radiation of an argon ion laser was recorded photoelectrically in the region 5200-8500 AA on a SPEX 0.85 m double monochromator. Using the measured intensities of P(17) rotational lines of thirty-eight ( nu '=43, nu ) bands and the Franck-Condon factors based on the recent molecular data of the B and X states, the variation of the square of the electron transition moment, mod M(R) mod 2, with R centroid in the range R=2.65-3.09 AA was studied. It was noticed that the electronic transition strength has a maximum value at R=2.83 AA and is represented by the relation mod M(R) mod 2=constant(-500.358+377.125R-38.483R2-25.429 R3+4.9831R4). Present results are discussed in relation to those obtained from earlier studies.

Investigation of Electronic Transitions Probabilities of SiCl

Abstract Absorption spectra behind the incident shock wave in a gas mixture of SiCl4:Ar were investigated. Two systems of SiCl: B2σ+−X2π and B12Δ-X2σ molecular bands were revealed. The continuous absorption in the range of 300–345 nm is assigned to the spectrum of SiCl2. The B2π+−X2π and B12Δ-X2π electronic transition strengths of the SiCl molecule were determined from the absolute intensity mensurements. The following, values viere obtained:

Current state of research into the radiative characteristics of diatomic molecules

The review describes the current state of studies of radiative characteristics for diatomic molecules. The problems arising in describing the intensity distribution in the adiabatic approximation and possible ways of their solutions are discussed. The progress achieved in the theoretical calculations of electronic transition probabilities, Franck—Condon factors and Honl—London factors, as well as in the experimental determination of electronic transition strengths and the lifetime of electronically-excited states, is demonstrated. The results of studies are discussed.

Probabilities for electronic transitions of molecular systems of high-temperature air components—II. The γ and β systems of NO and the (4+) system of CO

Literature results on absolute and relative probabilities for electronic transitions and on lifetimes of electronically excited states in the γ and β systems of the NO molecule and in the (4+) system of the CO molecule are critically analyzed. The results of previous studies to establish the dependence of the electronic transition strength on the r-centroid for these molecular systems are shown to be inadequate. Using a combined analysis of absolute and relative probabilities, new normalized functions S e ( r v′ v″ ) are obtained that describe the behaviour of the transition strengths in the spectral ranges occupied by the γ and β systems of NO and by the (4+) system of CO.

Probabilities for electronic transitions of molecular systems of high-temperature air components—I. The schumann-runge system of the O 2-molecule and the first positive system of the N 2-molecule

The results for absolute and relative probabilities for electronic transitions of the Schumann-Runge system of the O 2-molecule and the first positive system (1+) of the N 2-molecule published elsewhere have been critically analyzed. For the S-R system, statistical processing of the experimental results for absolute and relative probabilities on a joint basis made it possible to establish a new dependence of the electronic transition strength on the internuclear separations S e ( r v′ v″ ), which reliably describes the behaviour of S e over the whole spectral range. For the (1+) system of the N 2-molecule, it has been shown that none of the published dependences S e ( r v′ v″ ) provide acceptable fits to the measured results on absolute intensities and life-times. In practical calculations, one should use the dependence given in Ref. 41, which is derived from relative intensities and corroborated by absolute intensity measurements.

Study of non-linear extrinsic luminescence in GaAs. II. The role of auger recombination

The excitation intensity dependence of the 0.99, 1.03, 1.2, and 1.3 eV extrinsic emission in heavily doped n-type GaAs crystals (n0 = 5 × 1017 to 2 × 1018 cm−3) is studied at 77 to 300 K. An analysis is given in which a functional intensity dependence of the extrinsic emission on a rate of simultaneous radiative and non-radiative electronic transitions in radiative centres is considered. Linear and superlinear 0.99, 1.03, 1.2, and 1.3 eV extrinsic emission is observed at low temperatures depending on the strength of non-radiative electronic transitions in radiative centres studied. The main features of non-linear extrinsic emission (superlinear emission increase with excitation intensity, a shift of emission quenching curves to lower temperatures as excitation intensity is increased, a change from the superlinear to a linear excitation dependence of emission intensity as temperature is raised) are satisfactorily explained by a model which includes strong non-linear, in intensity, dependence, radiationless transitions in radiative centres. The model discussed takes into account a decrease in the rate of non-radiative electronic transitions in radiative centres as the exciting light considerably changes the electron occupancy of defects associated with the centres studied; as a result the internal quantum efficiency and emission decay time for the luminescence bands are increased as excitation intensity is raised. [Russian text Ignored]

Spectroscopy of EDA Complexes at High Pressures. II. Absorption of Several TCNE Complexes in Polymer Matrices

The charge-transfer absorption of 12 aromatic-hydrocarbon—TCNE molecular complexes in polymer matrices has been studied in the 0–25-kbar range. The observations for these solid solutions are compared with the results for compressed liquid solutions obtained by Gott and Maisch. The spectral shifts in the charge-transfer-band maxima range between +540 and −1700 cm−1 at 25 kbar for the complexes containing the various donors. A 1.1–3.5-fold increase in intensity at 25 kbar can be related directly to electronic transition strengths without applying corrections for complexation equilibria as required in liquid solutions. The bandwidths of the charge-transfer bands appear insensitive to compression. A comparison of the pressure influence on the spectral characteristics of molecular complexes and of the free donors suggests that for complexes the effects from solvent interactions are overshadowed by strong charge-transfer forces which are highly specific in nature.

Charge transfer model for alkali halide electronic transition strengths

A simple one-electron charge transfer model due to Mulliken is applied to alkali halide molecules to estimate the relative amount of parallel and perpendicular character in the “bundles” of unresolved electronic transitions which lead to dissociation and produce a normal or an excited alkali atom. If the bonding in the ground state is “purely ionic” and that in the excited state is “purely atomic,” the model indicates that most of the intensity will appear in perpendicular transitions. If the ionic and atomic character are mixed equally, however, the parallel transitions pre-empt all of the intensity, just as with purely covalent bonding. Even a slight amount of mixing (∼5%) is sufficient to put comparable intensity into the parallel and perpendicular transitions, in agreement with the scanty experimental evidence available. Numerical calculations are presented for the LiF molecule.