Hfs Components Research Articles

Large-sample study of uncertainty of hydrological model components over North America

The impacts of hydrological model components on performance and uncertainty of streamflow simulations are investigated using a multi-model approach over 698 catchments in North America. An ensemble of 180 different hydrological model structures is obtained by combining five snow models (SM), four potential evapotranspiration formulations (PET), three vertical (VFS) and three horizontal (HFS) flow rounting schemes. This study aims to first compare the multiple component combinations of SM, PET, VFS and HFS in terms of their ability at simulating streamflows for ten Köppen climate zones. A secondary goal is to evaluate the contribution of each model component to the total variance of the streamflow response according to the model structure for three streamflow metrics representing mean, high and low flows. Results indicate that there is no clear relationship between the structural and parametric complexity of the hydrological components and model performance for all three streamflow metrics. There is no single model structure which performs best in all climate zones and for all streamflow metrics. Streamflow uncertainty generated by the 180 synthetic hydrological model structures depends primarily on the metrics under study, but also on the climate zone. The evapotranspiration formulation is only critical for the mean flow metric. For the low-flow criterion, the VFS generates the most uncertainty and is therefore the most critical, whereas for the high-flow metric, performance is mostly related to the HFS component and SM for Nordic catchments. A better understanding of how hydrological model components generate uncertainty for a given climate and streamflow metric will lead to more robust model structures and therefore reduce the uncertainty of hydrological simulations.

Hyperfine structure measurements of neutral iodine atom (127I) using Fourier Transform Spectrometry

We report the hyperfine Structure (hfs) splitting observations of neutral iodine atom (II) in the 6000 – 10,000 cm−1 near infrared spectral region. The measurements were carried out using a high-resolution Fourier Transform Spectrometer (FTS), where an electrodeless discharge lamp (EDL), excited using microwaves, was employed as the light source and InGaAs as the light detector. A specially designed setup was used to lower the plasma temperature of the medium so as to reduce the Doppler width and consequently to increase the spectral resolution of hfs components. A total of 183 lines with hfs splitting have been observed, out of which hfs in 53 spectral lines are reported for the first time. On the basis of hfs analysis, we derived the magnetic dipole and electric quadrupole coupling constants, A and B respectively for 30 even and 30 odd energy levels and are compared with the values available in the literature. New hfs values for 5 even and 4 odd levels are also reported here for the first time.

Nitrogen nuclear spin flips in nitroxide spin probes of different sizes in glassy o-terphenyl: Possible relation with α- and β-relaxations

The pulsed electron-electron double resonance (ELDOR) technique was employed to study nitroxide spin probes of three different sizes dissolved in glassy o-terphenyl. A microwave pulse applied to the central hyperfine structure (hfs) component of the nitroxide electron paramagnetic resonance spectrum was followed by two echo-detecting pulses of different microwave frequency to probe the magnetization transfer (MT) to the low-field hfs component. The MT between hfs components is readily related to flips in the nitrogen nuclear spin, which in turn are induced by molecular motion. The MT on the time scale of tens of microseconds was observed over a wide temperature range, including temperatures near and well below the glass transition. For a bulky nitroxide, it was found that MT rates approach dielectric α (primary) relaxation frequencies reported for o-terphenyl in the literature. For small nitroxides, MT rates were found to match the frequencies of dielectric β (secondary) Johari-Goldstein relaxation. The most probable motional mechanism inducing the nitrogen nuclear spin flips is large-angle angular jumps, between some orientations of unequal occupation probabilities. The pulsed ELDOR of nitroxide spin probes may provide additional insight into the nature of Johari-Goldstein relaxation in glassy media and may serve as a tool for studying this relaxation in substances consisting of non-rigid molecules (such as branched polymers) and in heterogeneous and non-polar systems (such as a core of biological membranes).

Simultaneous coupling of three hfs components in a cascade scheme of EIT in cold 85Rb atoms

Abstract We have investigated multiple windows of electromagnetically induced transparency (EIT) registered in a cascade scheme 5S 1/2 (F = 3) → 5P 3/2 (F′ = 3) ↔ 5D 5/2 (F″ = 4, 3, 2) of cold 85 Rb atoms in a magneto-optical trap (MOT), with a weak probe laser in the first step and with a strong coupling laser in the second step. A structure composed of up to three transparency windows is observed in the spectral profile of the probe absorption, due to a simultaneous coupling of three F″ components of a dense hfs structure of a 5D 5/2 state of the 85 Rb isotope. The experimental EIT features, as dependent on the coupling beam intensity or on the frequency detuning from the F′ = 3 ↔ F″ = 3 resonance are compared with those theoretically obtained from a five-level model. A coefficient characterizing a relative decrease of absorption at the center of the most prominent EIT peak, plotted versus the coupling beam intensity, is also presented for both the experimental and modeled spectra. A good agreement between theory and experiment is observed. As it is very simple to manipulate the positions, shapes and depths of the EIT features, the present scheme could be of interest, e.g ., for the quantum information science.

The hyperfine and isotope structure of the Cd intercombination line – revisited

Careful analysis of the intercombination 51S0–53P1 line of the 113Cd isotope with two hfs components \(F'= \frac{1}{2} \rightarrow F'' = \frac{1}{2}\) and \(F' = \frac{3}{2} \rightarrow F'' = \frac{1}{2}\) was carried out. The hyperfine splitting of this line was determined to uncertainty less than 10-3 cm-1 using neon-perturbed Doppler limited spectra.

The Ag I and Au I Resonance Line Broadening in Helium Plasma

The shapes and shifts of the resonance spectral lines of neutral silver (Ag I: 328.068 and 338.289 nm) and gold (Au I: 242.795 and 267.595 nm) have been measured in a laboratory helium plasma of about 18,500 K electron temperature and an electron density ranging between 0.78 · 1023 and 1.24 · 1023 m−3. Stark broadening has been found as the dominant mechanism of the line shape and position formation. Our measured Ag I and Au I resonance line Stark widths (W) and shifts (d) are the first reliable experimental data. They are compared with calculated single Ag I and Au IW and d data based on a semiclassical approach. The measured values are higher than the calculated ones, especially of the Au I resonance lines. Besides, we have calculated the hyperfine structure (hfs) components and their relative intensities of the mentioned Ag I and Au I lines. Strong asymmetry between the red and blue components of the hfs was found. A modified version of the linear, low-pressure, pulsed arc was used as plasma source operated in helium with silver and gold atoms as impurities, evaporated from silver and gold cylindrical plates located in the homogeneous part of the discharge providing conditions free of self-absorption. At the above mentioned helium plasma conditions the splitting in the hyperfine structure (Δhfs) of the Ag I and Au I resonance lines has been overpowered by Stark and Doppler broadenings. We estimate that at electron densities below 1020 m−3 and electron temperatures below 10,000 K the hfs components in the 267.595 nm and 242.795 nm Au I lines play an important role in the line shape formation, and the resulting line profiles can be used for temperature estimation in optically thin plasmas

Hyperfine Structure Identification of Interstellar Cyanoallene toward TMC-1

Interstellar cyanoallene (CH2CCHCN) has been detected with the 100 m Green Bank Telescope (GBT) toward the dark Taurus molecular cloud (TMC-1) by means of the 414-313, 404-303, 515-414, and 505-404 rotational transitions at 20.2, 20.6, 25.2, and 25.7 GHz, respectively. The hyperfine structure (hfs) of the 414-313 transition is resolved; the remaining transitions have hfs components that are blended but are inferred owing to line width excesses atypical of TMC-1. An analysis of these four rotational transitions yields an average column density NT = 2.0(5) × 1012 cm-2 at an assumed rotational temperature of 4 K. The cyanoallene isomer methylcyanoacetylene (CH3CCCN) has previously been observed in TMC-1 and found to have a rotational temperature of ~4 K by other investigators. Using the GBT, the K = 0 and K = 1 structure of the JK = 5K-4K transition of methylcyanoacetylene was resolved toward TMC-1 and a total column density of NT = 4.5(4) × 1011 cm-2 was obtained for the 4 K rotational temperature. Thus, cyanoallene appears to be more abundant than methylcyanoacetylene toward TMC-1 by a factor of ~4.5. The implications of this result are discussed in terms of relative bonding energy differences and possible differences in formation chemistry.

Experimental study of the resonance radiation group delay in degenerate systems

The dependence of the polarization-and intensity-modulation group delay on the polarization of electromagnetic wave was studied experimentally for different transitions between the hfs components of the 87Rb D 1 absorption line. It was found that the polarization-modulation delay strongly depends on the degeneracy structure of resonant transition and, in the general case, on the ellipticity of light-wave polarization. It is demonstrated that the polarization-modulation delay does not occur for the transitions not involving dark states. The polarization delay was studied as a function of the polarization ellipticity angle. The intensity-modulation delay was measured for the resonance radiation to show that it is observed for all 87Rb D 1-line transitions and is independent of polarization.

Frequency stabilization of Nd:YVO4 mini-laser using the third-harmonic detection

Via saturated absorption spectroscopy and the third-harmonic detection technique, the hyperfine spectra of 127I2 near 532 nm have been observed within the tuning range of a mini Nd: YVO4-KTP laser. The laser is frequency stabilized against one hyperfine structure (hfs) component of 127I2. The analysis of error signal shows that it is possible to realize a frequency stability of 3.0 × 10−13 at 1 s average time.

Higher order Stark effect and transition probabilities on hyperfine structure components of hydrogen like atoms

A quantum-electrodynamical (QED) perturbation theory is developed for hydrogen and hydrogen-like atomic systems with interaction between bound electrons and radiative field being treated as the perturbation. The dependence of the perturbed energy of levels on hyperfine structure (hfs) effects and on the higher-order Stark effect is investigated. Numerical results have been obtained for the transition probability between the hfs components of hydrogen-like bismuth.

Ultra–High‐Resolution Observations of Interstellar Naiand CaiiK toward the High Galactic Latitude Star HD 28497

We present very high resolution (0.32 km s-1) spectra of interstellar Na I D1, D2, and Ca II K absorption toward HD 28497 obtained with the Ultra-High-Resolution Facility at the 3.9 m Anglo-Australian Telescope. The star is located in projection in a highly disturbed interstellar region close to a number of identified features including the high galactic latitude molecular cloud MBM 20, the large Orion-Eridanus shell, seen in Hα and H I 21 cm maps, and a filamentary loop structure between vLSR = -12 and -4 km s-1 in the Berkeley H I 21 cm survey and visible on the IRAS 100 μm map. Toward HD 28497 we detect 13 absorption components in the Na I spectra, to a column density limit of 2 × 1010 cm-2, and 10 in Ca II K over a velocity range of ~70 km s-1. Four absorption components in the Na I spectra show s-resolved hyperfine structure with b-values from 0.31 to 0.40 km s-1 and column densities from 4.0 to 14 × 1010 cm-2. If we assume the clouds represented by these components have no internal turbulent velocities, their temperatures would range between 134 and 227 K. One of these hyperfine split (hfs) components, at vLSR = -11.1 km s-1, shows significant temporal variation in equivalent width compared to earlier (1977) observations, making this the first interstellar sight line outside the Vela supernova remnant to show a time-varying component. The feature may be associated with the filamentary loop structure seen in this region. There is poor correspondence between the Na I and Ca II profiles: we do not detect narrow Ca II profiles to the four hfs Na I components, and only three of the well-resolved components have the same Ca II and Na I radial velocities and consistent b-values. One of these components, at vLSR = -30.0 km s-1, has a low Na I/Ca II ratio and arises in a region where turbulent motions dominate—properties consistent with the hypothesis that the cloud lies close to HD 28497. In general, however, the Na I and Ca II occupy different gaseous phases in the ISM. We have compared our data with 21 cm emission profiles obtained from the recent Leiden/Dwingeloo H I survey. Based on agreement in the velocities, the Na I/Ca II ratio, and the kinetic temperatures, we conclude that the component at vLSR = -7.5 km s-1 is associated with the front side of the large, expanding Orion-Eridanus shell. Unexpectedly, the molecular cloud MBM 20 is not detected either in our absorption spectra or in the H I profiles, indicating that HD 28497 lies away from the core of MBM 20. Apart from the two features at -11 and -7.5 km s-1 there is almost no agreement between the H I profiles and the optical spectra. Although we cannot rule out the possibility that most of the H I lies behind the star, this explanation seems unlikely because many of the H I features have previously been attributed to foreground phenomena. The beam sizes of the H I and the optical studies are quite different and this suggests a different explanation, namely that the physical sizes of the interstellar structures we detect in Na I and Ca II are not extensive enough to be detected in H I. If so, this raises questions about the usefulness in general of combining results obtained from H I 21 cm studies with results obtained from optical (or ultraviolet) studies of the interstellar gas.

Second-order Zeeman effect of theX?B transition in molecular iodine

Saturated absorption spectroscopy was applied to study the line shape of the molecular iodineX(ν″ = 0,J″ = 13,15) →B(ν′ = 43,J′ = 12, 16) transition (λ = 514.5 nm) in a transversal magnetic field as high as 0.51 T. The Zeeman structure of several hyperfine structure (hfs) components was completely resolved and a detailed study of the second-order Zeeman shift and splitting was made. The anisotropic Magnetic Susceptibility (MS) of the molecular iodine both in theB(43) (X′ = 7.3 ± 1 × 10−34 J/Oe2) and theX(0) [χ″ = (0.6 ± 1) × 10−34 J/Oe2] states as well as the isotropic MS difference [χ′0 −χ″o = (2 ± 0.2) × 10−34 J/Oe2] was measured.

Measurement of the transverse Doppler shift using a stored relativistic7Li+ ion beam

We have performed for the first time precision spectroscopy on a coasting fast7Li+ ion beam in a storage ring. The ion beam moving with 6.4% speed of light was first electron cooled and then merged with two counterpropagating laser beams acting on two different hyperfine transitions sharing a common upper level (λ-system). One laser was frequency locked to thea 3 127J2 hfs frequency component established as a secondary frequency standard at 514 nm. The second laser was tuned over theλ-resonance, which was recorded relative to127J2 hfs components. This experiment is sensitive to the time dilation in fast moving frames and will lead to new limits for the verification of special relatively. The present status of the experiment and perspectives in accuracy are discussed.

The nature of the paramagnetic centres at g = 2.0057 and g = 2.0031 in marine carbonates

A number of ESR signals appears regularly in marine carbonates with characteristic properties ( g -factor, line width, symmetry). In this study we try to clarify the nature of the signals at g = 2.0057, 2.0031, and 2.0036 which are relevant for ESR dating. Especially the knowledge of the nature of the centre with g = 2.0057 may enable one to obtain reliable age information from this signal. Our approach was to synthesize carbonate powders (with different Mg/Ca ratios) doped with varying concentrations of SO 2− 3 ions (or other sulphur compounds). On irradiation the samples with a Mg/Ca ratio > 0.1 showed very intense, isotropic ESR signals at g = 2.0057 and 2.0031. The intensity of both signals was found to be related to the SO 2- 3 concentration. By measuring the corresponding HFS components from natural 33 S ( X -band and Q -band) we could unambiguously assign these signals to SO − 2 ( g = 2.0057) and SO - 3 ( g = 2.0031) radicals. The number of radicals related to the isotropic signals have been shown to be positively correlated to the Mg content of the carbonates. At low Mg content an axial signal ( g per = 2.0036; g per = 2.0021) arises, probably also originating from SO − 3 . Experiments at various cavity temperatures indicate that the isotropic signals are due to rapid tumbling radicals (room temperature), thus generating motional narrowed lines. At lower temperatures (< − 100°C) the tumbling of the radicals will be blocked and the corresponding anisotropic species can be detected exclusively. Comparing the properties ( g -factor, line width, MW saturation, temperature behaviour, response to irradiation and annealing) of the ESR signals in question with those in natural carbonates we deduce that they originate from the same paramagnetic centres in both cases.

Hyperfine structure of the lower configurations in Y II by fast ion beam-laser spectroscopy

The hyperfine structure (hfs) of levels in the configurations 4d5s, 4d2 and 4d5p in Y II has been recorded using fast ion beam-laser spectroscopy. The levels in the 4d5s configuration were excited with frequency doubled laser light to levels in the 4d5p configuration, whereas the levels in the 4d2 configuration were excited by visible laser light. All hfs components could not be observed in the spectra, and therefore the magnetic dipole coupling constants A were evaluated in a parametrization of the peak separations in the framework of the effective operator theory.

From linear amplification to triggered superradiance : illustrative examples of stimulated emission and polarization spectroscopy for sensitive detection of a pulsed excited forbidden transition

This paper presents our experimental strategy for detecting an electric-field controlled pulsed-excited highly forbidden transition such as the 6S-7S transition of the Cs atom. The amplification of a pulsed probe beam close to resonance for one hfs component of the 7S – 6P3/2 transition is monitored. Furthermore the polarization modification experienced by the probe beam as a result of its interaction with the vapor is meticulously analysed. In convincing examples we point out the high sensitivity and complete selectivity of the method for the angular anisotropy of the 7S state, such as orientation or alignment created in the 6S-7S excitation process. We illustrate the flexibility of the method by varying the pump-probe delay, or by changing the relative positions of the beams or the magnitude of the E-field that directly controls the optical gain. A smooth transition from linear amplification to triggered superradiance is observed which necessitates readjustment of the probe intensity for optimal detection. We demonstrate the vapor-induced enhancement of the amplification anisotropy, expected at high optical density.

Iodine-stabilized He-Ne Lasers at λ = 633 nm of a Compact Construction

The paper deals with He-Ne lasers at 633 nm, frequency-stabilized by saturated absorption in 127I2. The procedure of iodine cell cleaning and filling is presented in detail. This technology provides long-term reproducibility of laser frequency as may be seen from measurements taken over a four-year period. The paper shows the hyperfine spectrum of a fused silica laser with eighteen hyperfine components obtained by a third-harmonic detection technique and mean frequency differences resulting from comparisons with the standards of the PTB (Braunschweig) and the BIPM (Paris). The frequencies of the line centres of hyperfine structure (hfs) components o, p, q, r of the R (127) 11-5 absorption line of 127I2 measured directly by beat frequency measurement are presented. Taking into consideration that the measured laser has a mean frequency offset of -22 kHz for hfs components (a-n), the following frequency differences of the components o, p, q, r with reference to the component i of the reference laser INVAR 1 have been obtained: δνoi = (-263,187 ± 0,01) MHz δνqi = (-292,689 ± 0,05) MHz δνpi = (-290,271 ± 0,05) MHz δνri = (-320,720 ± 0,01) MHz. The He-Ne/I2 lasers have been used for testing the single-frequency-stabilized lasers.

Radiation transport within the natural isotopic mixture of rubidium vapor after isotope selective excitation

The radiation transport within the natural isotopic mixture of rubidium is studied by detecting the time dependent resonance fluorescence after isotope selective excitation of87Rb or85Rb to the 52P3/2 state by the pulsed light of a laser diode. At atomic densities of about 1012 cm−3 the mean number of photon scatterings is 10 or 25 after excitation of87Rb or85Rb, respectively. Monte Carlo simulations of multiple photon scattering are used to reproduce the time dependent fluorescence signals. Satisfactory agreement between experiments and calculations can be achieved only if a radiative transfer of excitation energy between the different isotopes is considered. The energy transfer can be explained by radiative coupling of the different isotopes due to two partially overlapping hfs components of the 780 nm resonance line. As a test of our theoretical approach fluorescence signals recorded after excitation of87Rb and85Rb under identical experimental conditions are fitted both by using the same set of two parameters.

Intercomparison of I2-Stabilized He-Ne Lasers (λ = 633 nm) of the Institute of Scientific Instruments, CSSR, and the Physikalisch-Technische Bundesanstalt, FRG

The frequencies of six iodine-stabilized He-Ne-lasers developed at the UPT have been compared with one of the PTB lasers. The lasers were operated at λ = 633 nm. Their frequencies were stabilized to the line centres of hyperfine structure (hfs) components of the R(127) 11-5 absorption line of 127I2 using the third-harmonic detection technique. The stabilized frequencies of the UPT lasers averaged for each laser over the four hfs components d, e, f, and g are distributed in two groups. The frequencies of one group of three lasers are close to the frequency of the PTB laser with maximum deviations of +4 kHz to -9 kHz. The frequencies of the other three lasers are offset by -38 kHz with deviations of +8 kHz to -4 kHz. The maximum frequency deviations between all six lasers are approximately one order of magnitude smaller than the uncertainties of the recommended wavelength values [1] for this laser system, demonstrating its high potential for the realization of the metre and for high-precision spectroscopy.

Saturation spectroscopy and OODR of NO 2 in a collimated molecular beam

With nonlinear saturation spectroscopy Lamb dips with line widths below 1 MHz were observed for visible transitions of NO 2 molecules in a collimated supersonic beam. Narrowly spaced hyperfine components which were overlapping in the linear sub-Doppler spectra with a residual Doppler width of 10 MHz could now be completely resolved. The application of optical-optical double resonance techniques allows the separate determination of lower state and upper state splittings and the recognition of mutually perturbing levels in the upper state. The analysis of the Lamb dip and the OODR spectra which show hfs components with Δ F=0, ±1 for P and R transitions confirms that an intermediate angular momentum coupling between cases b β S and b β J holds for the X 2A 1 ground state of NO 2 going towards case b β J with increasing J.