Range Of Quantum Numbers Research Articles

Comprehensive Data for Depolarization of the Second Solar Spectrum by Isotropic Collisions with Neutral Hydrogen

Abstract Interpretation of the second solar spectrum (SSS) requires a complete determination of the depolarizing effect due to collisions with neutral hydrogen. In this paper, we provide comprehensive collision data for simple atoms, complex atoms, and atoms with hyperfine structure. Grids of interaction potentials were computed for a large range of effective quantum numbers n* that characterize states of hypothetical simple atoms. After that, the Schrödinger equation is solved to calculate the collisional transition matrix for each value of n*. Thus, we constructed a database of collisional polarization transfer and depolarization rates of all p-, d-, and f-states of simple atoms. The obtained results are fitted to deduce 48 variation laws, leading to the determination of all depolarization and polarization transfer rates of solar simple atoms. These laws are general and can be applied for any simple atom. We demonstrate how these laws can be used to efficiently obtain the collision rates associated with complex atoms, as well as with atoms with hyperfine structure. We show how the reader may use the variation laws to reproduce all new (de)polarization rates of this paper, as well as all rates of our previous papers published since 2003. Accuracy of our variation laws is discussed. Our analytical laws can be easily implemented in the numerical models developed to simulate the formation of the SSS.

C6 coefficients for interacting Rydberg atoms and alkali-metal dimers

We study the van der Waals interaction between Rydberg alkali-metal atoms with fine structure ($n^2L_j$; $L\leq 2$) and heteronuclear alkali-metal dimers in the ground rovibrational state ($X^1\Sigma^+$; $v=0$, $J=0$). We compute the associated $C_6$ dispersion coefficients of atom-molecule pairs involving $^{133}$Cs and $^{85}$Rb atoms interacting with KRb, LiCs, LiRb, and RbCs molecules. The obtained dispersion coefficients can be accurately fitted to a state-dependent polynomial $O(n^7)$ over the range of principal quantum numbers $40\leq n\leq 150$. For all atom-molecule pairs considered, Rydberg states $n^2S_j$ and $n^2P_j$ result in attractive $1/R^6$ potentials. In contrast, $n^2D_j$ states can give rise to repulsive potentials for specific atom-molecule pairs. The interaction energy at the LeRoy distance approximately scales as $n^{-5}$ for $n>40$. For intermediate values of $n\lesssim40$, both repulsive and attractive interaction energies in the order of $ 10-100 \,\mu$K can be achieved with specific atomic and molecular species. The accuracy of the reported $C_6$ coefficients is limited by the quality of the atomic quantum defects, with relative errors $\Delta C_6/C_6$ estimated to be no greater than 1\% on average.

Experimental and theoretical study of core-excited3pndRydberg series of Mg

We present an experimental and theoretical study of the structure and autoionization dynamics of the ${(3{p}_{{j}_{\text{c}}}n{d}_{j})}_{J=1,3}$ core-excited Rydberg states of Mg. Spectra were recorded experimentally for principal quantum numbers $n$ in the range from 30 to 100 using the isolated-core-excitation technique. Large-scale configuration-interaction calculations combined with the exterior-complex-scaling method were also carried out, which do not rely on the assumptions used in the usual $R$-matrix multichannel-quantum-defect-theory treatment of core-excited Rydberg states. Agreement between theory and experiment is excellent over the entire range of principal quantum numbers studied and allows us to elucidate in detail the structure of the core-excitation spectra. The dominant autoionization mechanisms are identified, and in particular the very fast spin-orbit autoionization of some ${(3{p}_{3/2}n{d}_{j})}_{J}$ states above the $3{p}_{1/2}$ ionization threshold. We discuss the influence of the principal and total-angular-momentum quantum numbers $n$ and $j$ of the Rydberg electron and the total-angular-momentum quantum number $J$ of the atom on the autoionization dynamics. We also identify previously unobserved resonances attributed to members of the ${(3{p}_{{j}_{\text{c}}}n{g}_{j})}_{J}$ series.

Millimeter-wave spectroscopy of Zn I in triplet F Rydberg states

We continue our experiments on millimeter-wave spectroscopy of higly-excited Rydberg atoms with two valence electrons. In this work we have measured frequencies of 16 transitions between Rydberg triplet 4snf3FJ and singlet 4snd1D2, 4sng1G4 levels of neutral zinc (Zn I) in the frequency range 87–141 GHz and in the principal quantum number range n=30–37. The observed transitions were driven predominantly from triplet 4snf3F3 levels that were excited by a three-step laser excitation scheme 4s21S0 → 4s4p3P1 → 4s4d3D2 → 4snf3F3. The measured frequencies as well as those obtained in our previous work (Kutsenko et al., 2015, J. Phys. B: At. Mol. Opt. Phys. 48, 245,005) were used to derive the Ritz expansion coefficients for triplet F states in the framework of the single-channel quantum defect theory.

X-ray spectra of the Fe-L complex

The Hitomi results on the Perseus cluster have led to improvements in our knowledge of atomic physics that are crucial for the precise diagnostic of hot astrophysical plasma observed with high-resolution X-ray spectrometers. However, modeling uncertainties remains, both within but especially beyond Hitomi’s spectral window. A major challenge in spectral modeling is the Fe-L spectrum, which is basically a complex assembly ofn ≥ 3 ton = 2 transitions of Fe ions in different ionization states, affected by a range of atomic processes such as collisional excitation, resonant excitation, radiative recombination, dielectronic recombination, and innershell ionization. In this paper we perform a large-scale theoretical calculation on each of the processes with the flexible atomic code (FAC), focusing on ions of Fe XVIIto Fe XXIVthat form the main body of the Fe-L complex. The calculation includes a large set of energy levels with a broad range of quantum numbernandl, taking into account the full-order configuration interaction and all possible resonant channels between two neighboring ions. The new data are found to be consistent within 20% with the recent individualR-matrix calculations for the main Fe-L lines, although the discrepancies become significantly larger for the weaker transitions, in particular for Fe XVIII, Fe XIX, and Fe XX. By further testing the new FAC calculations with the high-quality RGS data from 15 elliptical galaxies and galaxy clusters, we note that the new model gives systematically better fits than the current SPEX v3.04 code, and the mean Fe abundance decreases by 12%, while the O/Fe ratio increases by 16% compared with the results from the current code. Comparing the FAC fit results to those with theR-matrix calculations, we find a temperature-dependent discrepancy of up to ∼10% on the Fe abundance between the two theoretical models. Further dedicated tests with both observed spectra and targeted laboratory measurements are needed to resolve the discrepancies, and ultimately to get the atomic data ready for the next high-resolution X-ray spectroscopy mission.

Shift and Broadening of Atomic Circular States Induced by the Thermal Radiation

Analytical expressions for spontaneous and induced by blackbody radiation energy shifts and widths of atomic circular states are derived. The features of asymptotic behavior of the total width and energy shifts for highly excited Rydberg circular states in the blackbody radiation field are described. Approximate equations are proposed for simple evaluations of energy characteristics and an absence of temperature-independent spontaneous contribution to the total energy width in a range of high temperatures and principal quantum numbers is demonstrated.

Rotational rest frequencies of the low lying vibrational states of n-propyl cyanide from extensive laboratory measurements up to 506 GHz

Context. The spectra of four low-lying vibrational states of both anti and gauche conformers of normal-propyl cyanide were previously measured and analyzed in two spectral windows between 36 and 127 GHz. All states were then identified in a spectral line survey called Exploring Molecular Complexity with ALMA (EMoCA) toward Sagittarius B2(N) between 84.1 and 114.4 GHz with the Atacama Large Millimeter/submillimeter Array (ALMA) in its Cycles 0 and 1. Aims. We wanted to extend the measurements and analysis up to 506 GHz to provide accurate predictions over a much wider range of frequencies, quantum numbers and energies. Methods. We carried out measurements in two additional frequency windows up to 506 GHz. Results. For the gauche conformer, a large number of both a- and b-type transitions were identified. For the anti conformer, transitions were predominantly, but not exclusively, a-type. We hence improved molecular parameters for the ground states of both anti- and gauche-n-propyl cyanide and for excited vibrational states of the gauche conformer (v30 = 1, v29 = 1, v30 = 2, v28 = 1) and anti conformer (v30 = 1, v18 = 1, v30 = 2, v29 = 1) with high order coupling parameters determined between v18 = 1 and v30 = 2. Parameters are published for the first time for v18 = v30 = 1 of the anti conformer and for v29 = v30 = 1 of the gauche conformer. Conclusions. In total 15385 lines have been incorporated in the fits and should allow good predictions for unperturbed lines over the whole operating range of radio-telescopes. Evidence is found for vibrational coupling for some levels above 380 GHz. The coupling between v18 = 1 and v30 = 2 of the anti conformer has been well characterized. An additional list of 740 lines showing potential but as yet unidentified coupling has been provided for astrophysical identification.

Сдвиг и уширение циркулярных состояний атома тепловым излучением

Analytical expressions for spontaneous and induced by blackbody radiation energy shifts and widths of atomic circular states are derived. The features of asymptotic behavior of the total width and energy shifts for highly excited Rydberg circular states in blackbody radiation field are described. Approximate equations are proposed for simple evaluations of energy characteristics and an absence of temperature-independent spontaneous contribution to the total energy width in a range of high temperatures and principal quantum numbers is demonstrated.

Observation of Rydberg Blockade Induced by a Single Ion.

We study the long-range interaction of a single ion with a highly excited ultracold Rydberg atom and report on the direct observation of an ion-induced Rydberg excitation blockade mediated over tens of micrometer distances. Our hybrid ion-atom system is directly produced from an ultracold atomic ensemble via near-threshold photoionization of a single Rydberg excitation, employing a two-photon scheme that is specifically suited for generating a very low-energy ion. The ion's motion is precisely controlled by small electric fields, which allows us to analyze the blockade mechanism for a range of principal quantum numbers. Finally, we explore the capability of the ion as a high-sensitivity, single-atom-based electric field sensor. The observed ion-Rydberg-atom interaction is of current interest for entanglement generation or studies of ultracold chemistry in hybrid ion-atom systems.

Probing double Rydberg wave packets in a helium atom with fast single-cycle pulses

Fully quantum and classical calculations on a helium atom with two excited, radially localized Rydberg wave packets are performed. The differences between classical and quantum methods are compared for a wide range of principal quantum numbers to study the validity of the classical method for low-lying states. The effects of fast terahertz single-cycle pulses on an atomic system with one or two Rydberg wave packets are also studied using classical equations of motion. These results suggest that single-cycle pulses can be used as time-resolved probes to detect motion of the wave packets and to investigate autoionization properties.

Electromagnetically induced transparency of ultra-long-range Rydberg molecules

We study the impact of Rydberg molecule formation on the storage and retrieval of Rydberg polaritons in an ultracold atomic medium. We observe coherent revivals appearing in the retrieval efficiency of stored photons that originate from simultaneous excitation of Rydberg atoms and Rydberg molecules in the system with subsequent interference between the possible storage paths. We show that over a large range of principal quantum numbers the observed results can be described by a two-state model including only the atomic Rydberg state and the Rydberg dimer molecule state. At higher principal quantum numbers the influence of polyatomic molecules becomes relevant and the dynamics of the system undergoes a transition from coherent evolution of a few-state system to an effective dephasing into a continuum of molecular states.

Neon-, krypton-, and xenon-broadened spectral lines of water vapor

Intermolecular-interaction potentials for the H2O–Ne, H2O–Kr, and H2O–Xe systems have been determined from experimental broadening coefficients γ found for vibrational–rotational absorption lines in the ν2 band of water-vapor molecules in the corresponding mixtures at a temperature of T = 296 K. The rotational and vibrational corrections to the effective potentials are calculated. Broadening coefficients γ of the absorption lines of the H2O molecule are calculated for a wide range of rotational quantum numbers in the temperature range 300 K ≤ Т ≤ 600 K. A comparative analysis of the temperature dependences of the calculated broadening coefficients for the potentials in use is performed.

Excitation of Molecular Hydrogen in the Orion Bar PhotodissociationRegion from a Deep Near-infrared IGRINS Spectrum

Abstract We present a deep near-infrared spectrum of the Orion Bar Photodissociation Region (PDR) taken with the Immersion Grating INfrared Spectrometer (IGRINS) on the 2.7 m telescope at the McDonald Observatory. IGRINS has high spectral resolution ( R ∼ 45,000 ) and instantaneous broad wavelength coverage (1.45–2.45 μm), enabling us to detect 87 emission lines from rovibrationally excited molecular hydrogen (H2) that arise from transitions out of 69 upper rovibration levels of the electronic ground state. These levels cover a large range of rotational and vibrational quantum numbers and excitation energies, making them excellent probes of the excitation mechanisms of H2 and physical conditions within the PDR. The Orion Bar PDR is thought to consist of cooler high density clumps or filaments ( T = 50 – 250 K, n H = 10 5 – 10 7 cm−3) embedded in a warmer lower density medium ( T = 250 – 1000 K, n H = 10 4 – 10 5 cm−3). We fit a grid of constant temperature and density Cloudy models, which recreate the observed H2 level populations well, to constrain the temperature to a range of 600–650 K and the density to n H = 2.5 × 10 3 – 10 4 cm−3. The best-fit model gives T = 625 K and n H = 5 × 10 3 cm−3. This well-constrained warm temperature is consistent with kinetic temperatures found by other studies for the Orion Bar’s lower density medium. However, the range of densities well fit by the model grid is marginally lower than those reported by other studies. We could be observing lower density gas than the surrounding medium, or perhaps a density-sensitive parameter in our models is not properly estimated.

CO2-, He- and H2-broadening coefficients of SO2 for ν1 band and ground state transitions for astrophysical applications

The discovery of the Universe and of the interstellar medium (ISM) is based on the knowledge of the molecules that are present in those places. Most of our understanding about the composition of the ISM and planetary atmospheres has been made possible almost entirely thanks to spectroscopic observations. Sulfur dioxide, SO2, is one of the about 200 molecules that have been detected in the ISM or circumstellar shells. In addition to its astrophysical relevance, SO2 has a proved role in the Earth's atmosphere. It origins from biomass burning and volcanic eruptions and directly enters in the sulfur cycle. In this work high-resolution tunable diode laser (TDL) infrared (IR) spectroscopy and mm-/sub-mm wave spectroscopy are exploited to retrieve the broadening parameters of sulfur dioxide perturbed by H2, He and CO2. IR measurements are carried out for ν1 band transitions around 9 μm by using He and CO2 as damping gases. As far as the vibrational ground state is concerned, about 20 rotational transitions are analyzed by means of the speed dependent Voigt profile to retrieve H2- and He-broadening coefficients. From the experimental results some conclusions about the quantum number dependence of the H2-, CO2- and He-collisional cross sections are drawn. Both IR and MW experiments highlight a very weak dependence of He broadening parameters on the Ka and J rotational quantum numbers. In a similar way, also SO2-H2 broadening coefficients show a negligible dependence on the rotational quantum numbers. Conversely, when CO2 is employed as perturbing species, the observed collisional cross sections tend to decrease with increasing Ka values and to increase against J, at least over the range of quantum numbers considered. The present results provide the first systematic determination of line-by-line SO2-CO2 broadening coefficients and they are of relevance to increase the potential use of spectroscopic databases for astronomical applications.

Two-photon Rydberg resonances in lithium-7 obtained by recording reduction of resonance fluorescence

In a magneto-optical trap (MOT) of 7Li, two-photon Rydberg resonances are recorded by using a spectroscopic technique, which based on variation in the resonance fluorescence. The first excitation frequency is detuned by 0.59 GHz from the intermediate 2P 3/2 state. Two counter-propagating laser beams are used. The resonances are studied on two-photon transitions 2S 1/2 − nl in a range of principal quantum number n from 38 to 120. The widths of the observed resonances are varied from 4.4 to 13 MHz for different MOT parameters.

On algorithms for calculating the SVL-fluorescence spectra of polyatomic molecules

A software package for modeling the fluorescence spectra from a single vibrational level (SVL) of excited electron states under resonance laser excitation, in the adiabatic approximation with allowance for the “confusion” of normal coordinates under electron excitation, i.e., the Dushinsky effect, is presented. To algorithmize the calculation of the intensities in resonance fluorescence spectra, thirteen modules for the calculating Franck–Condon integrals are created. To optimize the calculation process, some simpler expressions are derived for the common terms of nested sums in the formulas for calculating Franck–Condon integrals from tone and overtone levels. To accelerate calculations, some constraints in the form of inequalities are additionally imposed on the range of vibrational quantum numbers in the ground electron state. The proposed algorithm for the modeling of SVL-fluorescence spectra of polyatomic molecules is based on quantum models of molecules in the ground and excited electron states calculated within the framework of contemporary ab initio quantum-mechanical methods and methods based on density functional theory.

High-resolution study of the yellow excitons inCu2Osubject to an electric field

We have used high resolution transmission spectroscopy to study the exciton level spectrum in Cu$_2$O subject to a longitudinal external electric field, i.e., in the geometry where the transmitted light is propagating along the field direction. Different experimental configurations given by the field orientation relative to the crystal and the light polarization have been explored. We focus on the range of small principal quantum numbers $n \leq 7$. The number of exciton states belonging to a particular principal quantum number increases with $n$, leading to an enhanced complexity of the spectra. Still, in particular for $n = 3 \ldots 5$ a spectral separation of the different lines is feasible and identification as well as assignment of the dominant state character are possible. We find a strong dependence of the spectra on the chosen light propagation direction and polarization configuration, reflecting the inadequacy of the hydrogen model for describing the excitons. With increasing the field excitonic states with different parity become mixed, leading to optical activation of states that are dark in zero field. As compared with atoms, due to the reduced Rydberg energy states with different $n$ can be brought into resonance in the accessible electric field strength range. When this occurs, we observe mostly crossing of levels within the experimental accuracy showing that the electron and hole motion remains regular. The observed features are well described by detailed calculations accounting for the spin-orbit coupling, the cubic anisotropy effects, and the symmetry-imposed optical selection rules.

STARK BROADENING OF HIGH-ORDER RADIO RECOMBINATION LINES TOWARD THE ORION NEBULA

ABSTRACT We report the results of observations and analyses of 41 hydrogen radio recombination lines from the Orion nebula (M42) at 5.5 to 6.5 GHz, with a spectral sensitivity (channel-to-channel standard deviation) of . Observations were conducted at the Australia Telescope Compact Array. A 1 GHz bandwidth allowed simultaneous detection of up to 11 spectral lines of equal that were stacked to enable accurate measurement of line widths. Collisional widths in the range of principal quantum numbers n from 100 to 179 are found to be consistent with predictions of electron impact Stark broadening theory. An Orion nebula model with density inhomogeneities (clumps) and gradients of temperature and density is consistent with our data. We reanalyze the data of Smirnov et al. and Bell et al. and find excellent agreement between all statistically significant measurements and theory. Our findings confirm the absence of line narrowing for n = 100...179.

Semi-classical calculations of self-broadening coefficients of OCS and HCN at temperatures between 200 K and 298 K

For some temperatures of atmospheric interest from 200 to 298K, the self-broadening coefficients of OCS-OCS and HCN-HCN collisional systems, at different strengths of electrostatic interactions, were calculated respectively for ν1 and ν2 bands for a wide range of rotational quantum numbers J. In particular, we have considered some lines that were not studied previously. We have employed the approximation of bi-resonance functions (Starikov, 2012) in the frame of the semiclassical model of Robert and Bonamy with exact trajectory (RBE).The calculated results are found to be fully consistent with the available experimental values of self-broadening coefficients of OCS and HCN. A comparative study shows that the RBE calculations reproduce the dependence of broadening coefficients on quantum number J much better than the simpler Robert and Bonamy model with parabolic trajectory (RB) for all considered temperatures.

Improved measurements and analysis of the far-infrared spectrum of methanol-D1 (CH2DOH) arising from trans- (e0) to gauche- (e1 & o1) states

In this work the millimeter-wave (MMW) and far infrared (FIR) absorption spectrum for the asymmetrically deuterated Methanol (CH2DOH) species measured recently at a temperature of −60°C with better accuracy and signal/noise (S/N) ratio than known before has been assigned for transitions originating at the lowest lying trans- to gauche-states. The entire spectrum for 50–1200cm−1 has been re-recorded recently using the Synchrotron Radiation Source coupled with the Bruker Fourier Transform Infrared (FTIR) spectrometer with a resolution of about 0.001cm−1 or better. Complete spectrum has not been exploited a great deal but it helped to entangle overlapping lines in the present work. This also fills the gap remaining in the usual FTIR in the range 400–500cm−1. Hence it is expected to help the interacting partner for the Coriolis interaction encountered earlier. The assigned transitions mostly for the axial rotational angular momentum quantum number K+1←K, both for R- and Q-sub bands for wide range of rotational angular momentum quantum number. The MMW spectrum has been recalibrated and assigned for a number of Q-branches. The assignments are confirmed rigorously using closed loop residual technique. The assigned rR and rQ lines have been analyzed in terms of polynomial expansion parameters. The new assignments are presented for about 750 transitions and a grand atlas of more than 1000 lines has been prepared which will be made available through the open source server at “research gate”. The present work should be useful in the area of astrophysical detection and further understanding of the energy relaxation pathways in the molecule.