Experimental Energy Levels Research Articles

Towards Efficient Blue Delayed-Fluorescence Molecules by Modulating Torsion Angle Between Electron Donor and Acceptor

Towards Efficient Blue Delayed-Fluorescence Molecules by Modulating Torsion Angle Between Electron Donor and Acceptor

Ro-vibrational levels and their (e-f) splitting of acetylene molecule calculated from new potential energy surfaces

Ro-vibrational energy levels of acetylene are reported using variational nuclear motion calculations from new ab initio and empirically optimized full six-dimensional potential energy surfaces in the ground electronic state of the acetylene molecule. The calculations account for the triple, quadruple and quintuple excitations as well as relativistic and diagonal Born-Oppenheimer corrections. Variational nuclear motion calculations were performed using the exact kinetic energy operator in orthogonal coordinates. The convergence of energy levels calculations versus the size of the vibrational basis set functions was verified. Our best ab initio potential energy surface that includes the above-mentioned contributions provides the RMS (obs.-calc.) errors of 0.95 cm−1 for five fundamental energy levels. The largest contribution to the RMS error is caused primarily by a significant deviation of the ν4 fundamental frequency. Experimental values of 120 vibrational band origins were used to empirically adjust few lower-order parameters of the potential energy surface. The average error drops down to 0.45 cm−1 or 0.25 cm−1 for empirically optimized potential energy function with two or seven adjusted parameters corresponding to quadratic force field terms and one third order term. The splitting of (e – f) rovibrational doublets and their J dependence were calculated with high accuracy due to the full account of Coriolis interactions. Computed (e – f) splittings allow one to check the correctness of the assignment of empirical energy levels. The estimation of the accuracy for the calculated vibrational levels in an extended range up to 9500 cm−1 shows that the set of ab initio vibrational levels can be used for future assignments of empirically not observed ro-vibrational energy levels. The comparison of the calculated and experimental ro-vibrational energy levels of the C2D2 and 13C2H2 isotopologues is also reported.

Zeeman and laser site selective spectroscopy of C1 point group symmetry Sm3+ centres in Y2SiO5: a parametrized crystal-field analysis for the 4f 5 configuration

Parametrized crystal-field analyses are presented for both the six and seven fold coordinated, C1 symmetry Sm3+ centres in Y2SiO5, based on extensive spectroscopic data spanning the infrared to optical regions. Laser site-selective excitation and fluorescence spectroscopy as well as Zeeman absorption spectroscopy performed along multiple crystallographic directions has been utilized, in addition to previously determined g tensors for the 6H5/2Z1 and 4G5/2A1 states. The resultant analyses give good approximation to the experimental energy levels and magnetic splittings, yielding crystal-field parameters consistent with the few other lanthanide ions for which such analyses are available.

Experimental and optical studies of the new organic inorganic bromide: [(C3H7)4N]2CoBr4

The alkylammonium halogenocobalate families are subjected to diverse studies according to their wide field application. In this work, the [(C3H7)4N]2CoBr4 compound was synthesized using a slow evaporation solution growth method at room temperature and characterized by X-ray powder diffraction (XRPD) and UV-VIS-IR absorption spectrometry. The X-ray powder diffraction (XRPD) data confirmed the formation of a single-phase with monoclinic system (C2/c space group). The optical absorption and reflectance spectra of the named compound were measured at the range [240 nm–1900 nm] at room temperature. Using three methods, we have determined the direct optical band gap estimated at 3.8 eV and the Urbach energy. Different models were used to calculate the refractive index, which was found to be in the range of 2.12–2.58. This spectrum consists also of electronic transition d-d of Co2+ (3 d7) ions. This work examines a detailed crystal-field analysis of the UV–Vis–NIR lines associated to the transitions between the Stark levels of Co2+, occupying a Td site symmetry in [CoBr4]2- (organic part). The theoretical study is based on the Racah tensor algebra methods. This analysis permits us to determine the electronic structure of the cobalt ion Co2+ based on the crystal field theory. As a result, Racah and crystal-field parameters have been reliably obtained. A good agreement between the theoretical and the experimental energy levels are obtained. This theoretical study confirms the Td site symmetry of Co2+ in [CoBr4]2- and leads to a satisfactory correlation between experimental and calculated energy levels. In addition to internal transitions, the absorption spectrum shows vibrational peaks witness of anharmonic behavior.

Isotropic and anisotropic collision-induced light scattering spectra of krypton gas simultaneously fitted by ground state interatomic potential

Isotropic and anisotropic binary collision-induced light scattering spectra of gaseous krypton obtained at room temperature are analyzed in terms of different interatomic potentials, both reference and recent, and trace and anisotropy models of interaction-induced polarizability. The spectral intensities obtained numerically at low frequencies are determined by bound and free transitions. At intermediate and high frequencies, the spectra are sensitive to both the attractive part of the potential and to short-range values of the trace or anisotropy. An empirical interatomic potential for the krypton gas interaction is developed by simultaneously fitting the Barker et al. (BFW) and modified Tang-Toennies (MTT) potentials to thermophysical and transport properties over a wide temperature range. The quality of the present potentials was checked by comparison between the calculated and experimental vibrational energy levels. The results show that these are the most accurate potentials reported to date for this system, both for the reproduction of spectral line shapes and spectral moments.

The study of some nuclear properties of even-even114-120Cd isotopes using interacting boson model-1

Nuclear properties of even-even 114-120Cd are studied in the framework of the interacting boson model (IBM-1). In this study, we have determined the most appropriate Hamiltonian for the study of even-even Cd (114-120) to calculate, its energy levels. The values of parameters have been determined using the (IBM1) Hamiltonian which yield the best fit to the available experimental energy levels. In addition, the backbending (moment of inertia as a function of (ħω)) of the energy levels for each isotope was indicated through the experimental and calculated values of the energy levels. A simulation program with MATLAP-18 has been built to obtain the theoretical energy levels for Cadmium isotopes with neutron number N=16, 18, 20 and 22 up to spin-parity 〖14〗_1^+,〖14〗_1^+,〖14〗_1^+,〖and16〗_1^+, respectively. The ratio of excitation energies of the first 4+ and the first 2+ excited states, R4/2 is also studied for the classification of symmetry of the nuclei. The results show that the 114-120Cd isotopes are γ – unstable rotor nuclei and they are dynamical symmetry O(6).

Three-phonon multiplets in 116Sn

Low-lying states in the even-even 116Sn nucleus have been studied by populating them using the 114Cd(α, 2n)116Sn reaction at the beam energy of 34 MeV. γγ coincidences, directional correlation ratio, and polarization asymmetry measurements were performed using the Indian National Gamma Array (INGA) with a digital data acquisition system. Three-phonon multiplets in the 116Sn nucleus have been investigated. The experimental energy levels are analyzed using theoretical approaches of the interacting boson model (IBM) in the U(5) limit and large-scale shell-model calculations using two different model spaces.

Determination of model potential parameters by fitting the numerical potentials from density functional theory

Analytical model potentials based on the single-active-electron approximation have been widely used in strong-field physics and attosecond science. In this paper, we determined potential parameters in the Tong–Lin’s model potential (Tong and Lin 2005 J. Phys. B: At. Mol. Opt. Phys. 38 2593) for neutral atoms (Z ⩽ 20), by fitting the numerical potentials calculated from the self-interaction-correction density functional theory and the fitting procedure is performed by the genetic algorithm. The reliability of these potential parameters is carefully examined by comparing the calculated orbital energies with those obtained from the Tong–Lin’s parameters and the term averaged experimental energy levels by taking He and Ar atoms for example. We further checked our fitted potential by comparing our calculated high-harmonic-generation and above-threshold-ionization spectra of He and Ar with those from both Tong–Lin’s parameters and the Laughlin’s model potential (Laughlin and Victor 1988 Adv. At. Mol. Phys. 25 163).

Optical studies of multiferroic HoCrO3 perovskite compound for optoelectronic device applications

The multiferroic HoCrO3 orthochromite compound was prepared using the sol-gel method. The optical properties of this ceramic were characterized by infrared (IR) and UV–Vis absorption spectroscopy. The IR spectrum shows a set of absorption peaks that can be assigned to the Cr–O and O–Cr–O vibrations. From UV–Vis absorption spectrometry, the reflectance spectrum and the Tauc model, reveal a direct and wide optical band gap evaluated at 3.34 eV and 3.206 eV respectively. The high value of the Urbach energy (528 ± 13) meV shows the presence of a high density of localized states. The extinction coefficient (k) was used to estimate the evolution of the refractive index n with the wavelength. Additionally, n obeys to Cauchy relation. Furthermore, the dispersion parameters were analyzed in the bases of Wemple and Di-Domenico model. The optical constants such as the skin depth and the optical conductivity were calculated and the results are discussed. From the UV–vis absorbance spectrum attributed to the d-d transitions of Cr3+ ion in HoCrO3, a theoretical crystal-field analysis is realized which leads to a good agreement between the calculated and the experimental energy levels. Furthermore, the electronic structure was compared with that obtained for Cr3+ ion in PrCrO3 ceramics. From Racah theoretical study, Tanabe Sugano Diagram and Photoluminescence measures, a transfer charge mechanism is proposed. The achieved results confirm the importance of our compound in optoelectronic device applications.

The length effect and color tuning of tetraphenylethylene functionalized oligothiophenes for effective detection of explosives

Aggregation-induced fluorescent materials are of great importance in optoelectronics and bioelectronics in solid-state devices. Herein, functionalized oligothiophenes were designed and synthesized with the tetraphenylethylene (TPE) groups to explore the length effect and color tuning for the effective detection of explosives. Remarkably, compounds 2TPE1T and 2TPE2T show an aggregation-induced emission phenomenon, while longer π–conjugated molecules 2TPE3T, 2TPE4T, TPE5T and 2TPE6T show aggregation-caused quenching character, where the reason has been explained based on UV–Vis spectra ranging from 378 to 446 nm. Furthermore, fluorescent titration experiments demonstrate that dye 2TPE1T has a better response than dye 2TPE2T for nitroaromatics. The visual detection limit of 2,6-DNT is 18.2 ng/cm2 in the test strip of 2TPE1T. In addition, there is an exquisitely linear curve between the theoretical and experimental energy levels for TPE functionalized oligothiophenes. The influence of introducing TPE end-capped on the energy gap convergence has also been discussed, showing the energy level correlation of linear fitting combined with a theoretical and experimental perspective. This result not only paves the way toward π–functional materials but also expands their applications.

Theoretical rovibronic spectroscopy of the calcium monohydroxide radical (CaOH).

The rovibronic (rotation-vibration-electronic) spectrum of the calcium monohydroxide radical (CaOH) is of interest to studies of exoplanet atmospheres and ultracold molecules. Here, we theoretically investigate the Ã2Π-X̃2Σ+ band system of CaOH using high-level ab initio theory and variational nuclear motion calculations. New potential energy surfaces (PESs) are constructed for the X̃2Σ+ and Ã2Π electronic states along with Ã-X̃ transition dipole moment surfaces (DMSs). For the ground X̃2Σ+ state, a published high-level ab initio PES is empirically refined to all available experimental rovibrational energy levels up to J = 15.5, reproducing the observed term values with a root-mean-square error of 0.06 cm-1. Large-scale multireference configuration interaction calculations using quintuple-zeta quality basis sets are employed to generate the Ã2Π state PESs and Ã-X̃ DMSs. Variational calculations consider both Renner-Teller and spin-orbit coupling effects, which are essential for a correct description of the spectrum of CaOH. Computed rovibronic energy levels of the Ã2Π state, line list calculations up to J = 125.5, and an analysis of Renner-Teller splittings in the ν2 bending mode of CaOH are discussed.

An experimentally-accurate and complete room-temperature infrared HCN line-list for the HITRAN database

A hydrogen cyanide line list (MOMeNT-90) developed for the HITRAN spectroscopic database covering 0–7500 cm−1 range (λ>1330 nm) is presented. The line list is a combination of the variationally calculated line intensities with line centers obtained from experimentally derived energy levels. There are four features of this line list which distinguishes it from the previously calculated ones. First, the intensities are variationally calculated using a new, high-accuracy potential energy surface (PES) obtained via fitting the PES using experimental energy levels. Second, a new ab initio dipole moment surface was calculated at a high level of quantum chemical theory. Based on the wave functions calculated with the new PES and use of the new dipole moment surface, line intensities are reported which of similar accuracy to those obtained experimentally. Third, the calculated states are mapped to the existing complete set of experimental eigenenergies, resulting in an assigned and complete HCN line list down to the HITRAN intensity threshold of 10−34 cm/molecule. Fourth, extensive validation of the line list is provided through line-by-line comparisons of the results with measured HCN spectra which confirms the accuracy of the intensities used to construct the line list. The line list is augmented with parameters needed to calculate line widths for pressure-dependent simulations.

Optical absorption properties of ZnF2-RO-TeO2 (R = Pb, Cd and Zn) glasses doped with chromium (III): Neuhauser model and crystal field study

Abstract Tellurite glasses with composition ZnF2-RO-TeO2 (R = Pb, Cd and Zn) containing 0.2 wt % of transition metal ions Cr3+ have been investigated for their structural and optical properties. The absorption spectra recorded for Cr3+-doped tellurite glasses indicate an octahedral coordination for the Cr3+ ions. These spectra show distinct features on the 4T2g(4F) absorption band due to the interaction of the 2Eg(2G) and 2T1g(2G) sharp levels with the vibrationally broadened 4T2g(4F) quasi-continuum via spin-orbit coupling called interference dips. This work analyz65es the dips using Neuhauser model in order to give a precisely values of the experimental energy levels of the broad band 4T2g(4F) and of the two 2Eg(2G) and 2T1g(2G) sharp levels. This analysis explains well the notion and the origin of the interference dips observed generally on the absorption spectra of the glasses. The parameters obtained from the Neuhauser model leads to information on the structure of the three glasses. From the experimental energy levels obtained by Neuhauser model, we examine a detailed crystal-field analysis of the visible lines associated to the transitions between the energy levels of Cr3+-doped tellurite glasses. The theoretical study is based on the Racah tensor algebra methods and leads to the electronic structure of the Cr3+ in the three glasses. As a result, Racah and crystal-field parameters have been reliably obtained and permit us to compare the intensity of the crystal field strength environment of Cr3+ in the three glasses. A good agreement between the theoretical and the experimental energy levels are obtained. The results of this work are compared with homolog glasses.

Vibrational levels of formaldehyde: Calculations from new high precision potential energy surfaces and comparison with experimental band origins

Vibrational energy levels of H2CO are reported using variational nuclear motion calculations from new ab initio and empirically optimized full 6-dimensional ab initio potential energy surfaces in the ground electronic state of the formaldehyde molecule. Ab initio calculations were carried out using extended electronic structure coupled-cluster calculations accounting for dynamic electron correlations including triple and quadruple excitations as well as relativistic and diagonal Born-Oppenheimer corrections. Variational nuclear motion calculations are compared in different sets of coordinates with exact kinetic energy operator and in normal coordinates with Watson-Eckart kinetic energy operator. Our best ab initio potential energy surface including the above mentioned contributions provides the RMS (obs.-calc.) errors of 0.25 cm−1 for fifteen vibrational band origins without empirically adjusted parameters. The average error drops down to 0.08 cm−1 for an empirically optimized potential energy function with six adjusted parameters corresponding to quadratic force field terms. The estimation of the accuracy for the calculated vibrational levels in an extended range up to 4500 cm−1 shows that the set of ab initio vibrational levels could be more consistent than experimental levels obtained from earlier studies of low resolution spectra. The comparison of the calculated and experimental vibrational energy levels of the D2CO isotopologue is also reported.

Thermochemical spin‐orbit corrections for platinum cation (Pt+)

AbstractIn quantum thermochemistry, many atoms require spin‐orbit corrections to compensate for the lack of spin‐orbit coupling in most calculations. When terms or configurations are strongly mixed, as they are in Pt+, naïve averaging of experimental data produces erroneous corrections. Here, spin‐orbit calculations provide the composition of observed energy levels in LS (Russell‐Saunders) terms. The compositional data are combined with the experimental energy levels to obtain averaged term energies for Pt+, including the ground‐term spin‐orbit correction. For ground‐state Pt+, a correction of (−4251 ± 136) cm−1 or (−50.8 ± 1.6) kJ mol−1 is recommended. The recommended value for the 2D‐4F excitation energy, which represents the nominal 5d‐6s promotion energy, is (7112 ± 225) cm−1. For anionic Pt−, simple J‐averaging is appropriate, and the ground‐state spin‐orbit correction is (−3896.4 ± 0.2) cm−1 or (−46.611 ± 0.002) kJ mol−1.

Experimental energy levels of 12C14N through marvel analysis.

The cyano radical (CN) is a key molecule across many different factions of astronomy and chemistry. Accurate, empirical rovibronic energy levels with uncertainties are determined for eight doublet states of CN using the marvel (Measured Active Rotational-Vibrational Energy Levels) algorithm. 40 333 transitions were validated from 22 different published sources to generate 8083 spin-rovibronic energy levels. The empirical energy levels obtained from the marvel analysis are compared to current energy levels from the mollist line list. The mollist transition frequencies are updated with marvel energy level data which brings the frequencies obtained through experimental data up to 77.3percent from the original 11.3percent, with 92.6percent of the transitions with intensities over 10-23 cm molecule-1 at 1000K now known from experimental data. At 2000K, 100.0percent of the partition function is recovered using only marvel energy levels, while 98.2percent is still recovered at 5000K.

Bose–Einstein condensation of dilute alpha clusters above the four-α threshold in 16O in the field theoretical superfluid cluster model

Abstract Observed well-developed $\alpha$ cluster states in $^{16}$O located above the four-$\alpha$ threshold are investigated from the viewpoint of Bose–Einstein condensation of $\alpha$ clusters by using a field-theoretical superfluid cluster model in which the order parameter is defined. The experimental energy levels are reproduced well for the first time by calculation. In particular, the observed 16.7 MeV $0_7^+$ and 18.8 MeV $0_8^+$ states with low-excitation energies from the threshold are found to be understood as a manifestation of the states of the Nambu–Goldstone zero-mode operators, associated with the spontaneous symmetry-breaking of the global phase, which is caused by the Bose–Einstein condensation of the vacuum 15.1 MeV $0^+_6$ state with a dilute well-developed $\alpha$ cluster structure just above the threshold. This gives evidence of the existence of the Bose–Einstein condensate of $\alpha$ clusters in $^{16}$O. It is found that the emergence of the energy level structure with a well-developed $\alpha$ cluster structure above the threshold is robust, almost independently of the condensation rate of $\alpha$ clusters under significant condensation rate. The finding of the mechanism that causes the level structure that is similar to $^{12}$C to emerge above the four-$\alpha$ threshold in $^{16}$O reinforces the concept of Bose–Einstein condensation of $\alpha$ clusters in addition to $^{12}$C.

Expert List of Absorption Lines of the SO2 Molecule in the 2000–3000 cm–1 Spectral Region

A detailed high-accuracy list of the SO2 molecule absorption lines was obtained in the 2000–3000 cm–1 spectral region, which is important for atmospheric applications, based on a combination of the high-accuracy data on experimental energy levels and variational calculations of the intensities of vibrational-rotational transitions. The expert list contains 70 565 absorption lines with an intensity cutoff 1.0E-27 cm/molecule. The results obtained are compared with the published data.

Spectroscopic study of K38 above the 31.67μs isomer

High-spin states of $^{38}\mathrm{K}$ above the $31.67\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s}$ (${\ensuremath{\tau}}_{m}$) isomer, populated through the $^{12}\mathrm{C}(^{28}\mathrm{Si},\phantom{\rule{0.16em}{0ex}}np)^{38}\mathrm{K}$ reaction with a 110 MeV $^{28}\mathrm{Si}$ beam, have been studied by using the Indian National Gamma Array (INGA) facility. Two new levels and four new transitions have been added to the existing level scheme. The spins and parities of most of the levels above the isomer have been assigned, modified, and confirmed from ${R}_{\mathrm{DCO}}$, ${R}_{\mathrm{ADO}}$, and linear polarization measurements. The multipole mixing ratios ($\ensuremath{\delta}$) for a few transitions have been measured. Large-basis shell-model calculations have been performed to understand the microscopic origin of these levels. In our calculations, different particle restrictions in $sd$- and $pf$-shell orbitals were used to reproduce the experimental level energies. Two-nucleon transfer spectroscopic factors have also been calculated for the levels above the isomer to support the new spin and parity assignments. Prediction of collective excitation at high excitation energy in $^{38}\mathrm{K}$ is also discussed.

Radiative Constants in the W VII Ion Spectrum

The probabilities of the 4 f 135p66p + 4 f 145p56p – 4 f 136s, 4 f 137s radiative transitions and the lifetimes of the 4 f 137s levels in the spectrum of the erbium-like W VII ion are calculated in the electric dipole approximation by the semiempirical intermediate coupling method using experimental energy levels known from the literature. The radial integrals necessary for calculating the absolute transition probabilities are obtained in the form of length with the Hartree–Fock functions.