Measuring magnetic fields in plasmas by means of light scattering

The theory of light scattering in plasmas containing a magnetic field yields the special case of modulated scattering spectra. The modulation frequency is governed by the field in the plasma and is equal to the electron cyclotron frequency. In this investigation magnetic fields in a plasma were determined by a laser scattering experiment. The experimental data were: electron densityn _e=10¹⁶cm^?3, electron temperatureT _e=3.2 eV, scattering angle θ=90 °, scattering parameter α=0.6, and a maximum field in the plasma of 125 kG. The spectrum measured at the maximum magnetic field was modulated with 3.6 × 10¹¹ Hz. In scattering experiments with a field reduced by about 20% the observed modulation frequency was 2.8 × 10¹¹ Hz. A thermal spectrum with a smooth profile was found when no field was present in the plasma. Applying the theory of cyclotron modulated spectra one obtains from the scattering experiment magnetic fields of 128, 100, and 0 kG. Within the experimental accuracy these values agree well with the fields determined by means of magnetic probes. Other possible interpretations of the measured deviations from thermal spectra (modulation with the plasma frequency or additional cold electron components in the plasma) are discussed, but they afford no explanation. This experiment has domonstrated that magnetic fields in plasmas can be measured locally and almost without disturbance by means of light scattering.     

Observation and analysis of the Xe−I collisional-pair photoassociation spectrum

The interpretation of the photoassociation spectrum arising in collisions of Xe and I atoms is refined with allowance for new data concerning the interaction potential of Xe and I collisional pairs. Spectroscopic constants for the XeI(B) state are determined:R′ _e =3.264961 Å,D′ _e =33,289.05 cm^?1,w′ _e =113.867826 cm^?1, andw′ _e x′ _e =0.238304 cm^?1.     

Spatial dependent diffusion of cosmic rays and the excess of primary electrons derived from high precision measurements by AMS-02

The precise spectra of Cosmic Ray(CR) electrons and positrons have been published by the measurement of AMS-02. It is reasonable to regard the difference between the electron and positron spectra(?Φ = Φ_(e-)-Φ_(e+)) as being dominated by primary electrons. The resulting electron spectrum shows no sign of spectral softening above 20 GeV, which is in contrast with the prediction of the standard model of CR propagation. In this work, we generalize the analytic one-dimensional two-halo model of diffusion to a three-dimensional realistic calculation by implementing spatial variant diffusion coefficients in the DRAGON package. As a result, we can reproduce the spectral hardening of protons observed by several experiments, and predict an excess of high energy primary electrons which agrees with the measurement reasonably well. Unlike the break spectrum obtained for protons, the model calculation predicts a smooth electron excess and thus slightly over-predicts the flux from tens of GeV to 100 GeV. To understand this issue, further experimental and theoretical studies are necessary.     

Rydberg states in the D layer of the atmosphere and the GPS positioning errors

The noncoherent radiation in the frequency range 0.8–8.0 (GHz) formed in the D layer of the ionosphere at high solar activity due to transitions between Rydberg states is considered. The emitting layer thickness located 80–110 km above ground surface is estimated. A complicated irregular behavior of the frequency dependence of the radiation intensity for different values of å electron concentration n _e and temperature T _e due to different characteristics of electron scattering on the nitrogen and oxygen molecules is revealed. The dependences of the flux power of UHF radiation from the D layer in the indicated frequency range on the concentration and temperature of free electrons are calculated. It is shown that, at a frequency of ν = 1.44 GHz, the UHF radiation spectrum features a characteristic waist point, the position of which is almost independent of the electron temperature T _e ; i.e., a one-parameter dependence of the power flux on the electron n _e density takes place. In the frequency range of 4.0–8.0 GHz, the radiation spectrum exhibits a family of curves that, for each value of n _e and a wide range of T _e , give rise to a relationship known as the “bottleneck.” It was found that, with increasing frequency, the bottleneck moves upwards along a curve described by a quadratic dependence on the radiation frequency. For a frequency of ～5 GHz, and a certain range of temperature T _e and electron concentration within 5 · 10³ cm^?3 < n _e < 2 · 10⁴ cm^?3, an almost linear dependence of the UHF radiation power on n _e is observed. A comparative analysis of GPS signal delays at frequencies ν _f ⁽¹⁾ = 1.57 and ν _f ⁽²⁾ ≈ 5 GHz for various states of the ionosphere is performed. It is shown that, under the same condition, the use of the second frequency is more advantageous and informative. The ways of further development of the theory and experiment in studying the role of quantum resonant properties in the distortion of global satellite positioning system signals and in solving the fundamental problem of their elimination are discussed.     

Electron screening in thed+3He fusion reaction

Cross section measurements of thed(³He,p)⁴He reaction have been extended to an energy as low asE _cm =5.4 keV. The data have an improved accuracy compared with previous work and confirm the existence of electron screening. The combined analysis of the present and previous data leads to an electron screening potential ofU _e =123 ± 9 eV. A similar analysis of previous data for³He(d, p)⁴He leads toU _e =186 ± 9 eV. Both screening potentials differ due to the molecular and atomic aggregate state of the targets involved in these investigations and are significantly larger than expected from available atomic physics models, supporting the general trend in studies of electron screening.     

Stark broadening of lines from multiply-charged carbon ions in a high-density arc plasma

Profiles of C(III) and C(IV) lines emitted in the VUV and visible regions from a pulsed arc (N_e=1.5×10¹⁸ cm^-3, T_e=5.3×10⁴K) have been measured with time resolution. The experimental results are in satisfactory agreement with the predictions of electron impact theory for (3-3) and (3-4) transitions for which the energy separation between the upper level and the nearest perturbing level is smaller than the electron thermal energy. For lines from (2-2) transitions for which the plasma is optically thick, damping constants determined experimentally agree with theoretical values within a factor of two.     

Short-living absorption and emission of CsI(Na)

This paper investigates the short-living absorption and the emission of CsI(Na) under a pulsed electron beam (Е_e=0.25 MeV, t_1/2=15 ns and W=0.003…0.16 J/cm²). The bands of singlet self-trapped excitons, as well as Na⁰ and V_k color centers have been detected in the transient absorption spectrum of CsI(Na). It has been found that the activator luminescence spectrum, peaking at 3.0 eV, fits a Gaussian (E_m=3.0 eV and FWHM=0.44±0.02 eV at 80 K) and remains the same at different time delays within 10⁻⁸-10⁻³ s. The decay kinetics of the 3.0 eV emission has one nanosecond exponential component and two microsecond ones with time constants 1.0 and 3.0 μs, which remain unchanged within 78-150 K. It is concluded that the activator emission is due to the radiative annihilation of sodium-perturbed two halide excitons from the non-relaxed singlet state. The pathways of such excitons creation are discussed.     

Verbreiterung von Hauptserienlinien des Kaliums durch Wechselwirkung mit Kalium- und Cäsiumatomen bei hohen Teilchendichten

For certain conditions the afterglow of low pressure discharges can be dominated by three body recombination. These conditions — electron densities of about 10¹² cm^?3 and electron temperatures of about 500 °K— are realized 20 μsec after switch off of the discharge for gas pressures (hydrogen) between 2 and 6 mTorr. In this pressure range the energy transfer from the electrons via the ions to the neutrals and subsequently to the wall is high enough to permit a decay of the electron temperature to low values before the electron density has decreased appreciably. A theoretical model demonstrates that the electron density decaydn _e/dt～n _e ³ f(T _e) is in good approximation equivalent todn _e/dt=const·n _e ² for a certain range of time and of parameters. This proportionality is observed. The measured values of the constant differ from the calculated ones by about 15%.     

The spectra and structure of indium iodide: The rotational and vibrational constants of the B 1 state

The rotational constants of the B 1 state of indium iodide are reported for the first time as B_e = 0.037533 cm⁻¹ and α_e = 0.000289 cm⁻¹ while T_e = 25050.60 cm⁻¹ for the B1-X0⁺ transition. Accurate vibrational constants are also computed from measured Q heads as ω_e= 146.36 cm⁻¹ and ω_eχ_e = 2.20 cm⁻¹.     

Mössbauer study of the hyperfine and magnetic properties of organo-di-iron electron reservoirs containing a polyaromatic bridging ligand

Organo di-iron electron reservoirs Fe(CP^*)₂(Ar) ⁿ⁺ withn=2, 1, 0, where Cp^* is C₅(CH₃)₅ and where Ar are the following bridges: biphenyl, dihydrophenanthrene, triphenylene, have been studied by Mössbauer spectroscopy in the solid state. Complexes withn=2, with 36e^? in the coordination spheres of the metals, exhibit the usual diamagnetic behaviour of 18e^?, Fe^II mono-iron systems. Complexes withn=1, 37e^?, are delocalized mixed valence (Fe^IIFe^I) with a spin 1/2; the magnetic hyperfine interaction, measured under an external field, shows equal delocalization of the 37^th e^? on the two iron centers and the two bridging carbon atoms of the biphenylene. Complexes withn=0, formally with 38e^?, have a practically temperature-independent quadrupole splitting, and isomer shift values which constrast with the expected behaviour of independent Fe^I, 19e^? centers. This indicates that the 37^th and 38^th electrons are mostly located on the polyaromatic bridge. Spectra obtained in an external field show a negligible magnetic hyperfine interaction and support this conclusion. In the case of biphenyl and dihydrophenanthrene bridges, this electron localization can be related to a strong intramolecular chemical coupling, evidenced by other spectroscopic and X-ray data [1].     

Collective states in 48V

The low-lying positive parity states of ⁴⁸V have been studied in the framework of deformed configuration mixing model calculations based on projected Hartree-Fock theory, within the full fp shell space. The modified Kuo-Brown effective interaction has been used. The calculated spectrum and the electromagnetic properties of these states are in good agreement with the experiment. The calculation predicts an excited low-lying collective K = 2⁺ band in the spectrum of ⁴⁸V and accounts for the observed breakdown of the “signature” selection rule arising in the shell-model calculation within the ($\text{f}\text{7}\text{2}\text{)}{}^{\mathrm{nd}}$ space. It does not favour a 5⁺ assignment to the observed 1.099 MeV level. Two sets of proton and neutron effective charges (i) e_p = 1.32e and e_n = 0.89e and (ii) Kuo and Osnes charges e_p = 1.25e and e_n = 0.47e were employed. The observed decay properties appear to favour the latter charges. Our model also explains in a semiquantitative way the observed K-value, moment of inertia parameter and the intrinsic quadrupole moment of the K = 1^?1 rotational band.     

Anomalous Cs I 5d-5⨍ lineshape in a non-debye plasma

Laser-induced cesium plasmas were diagnosed by emission spectroscopy, yielding electron densities in the range N_e = 10¹⁶?5 × 10¹⁷ cm^-3 and electron temperatures in the range T_e = 0.2-1 eV. The experimental lineshapes for T_e = 0.5 eV were found to be in good agreement with theory. For the more strongly coupled plasmas at N_e = 1-2 × 10¹⁶ cm^-3 and T_e = 0.2 eV, however, the Cs I 5d-5? lineshape was more asymmetric than predicted.     

Hot-wire measurements of the electron thermal conductivity in a potassium plasma

The electron thermal conductivity λ_e of a potassium plasma is found by measuring the electron heat flux in a hot-wire device placed in a magnetic field. In the range 2300–3000 K, λ_e (W/mK) = 0.906 X 10¹⁰ T^-2_e exp(-3.2 X 10⁴/T_e) at a plasma pressure of 800 Pa and a gas temperature T_a = T_e/1.3.     

Measurement of width and shift of rare gas lines emitted from a stock-tube plasma

In a diaphragm shock-tube, Ar, Kr and Xe plasmas were generated with equilibrium temperatures of 8,000 to 12,000 K. The electron densities were measured with a two-wavelength interferometer and varied from 4×10¹⁶ to 1.4×10¹⁷ cm^-3. Emission profiles of spectral lines were recorded with a polychromator setup in 1 μs intervals using a fast data acquisition system. Width w and shift d turned out to be proportional to electron density N_e for the observed lines. Stark broadening parameters w/N_e and d/N_e are presented for 3 Ar(I), 4 Kr(I) and 5 Xe(I) lines in the visible region of the spectrum.     

Radiative decay ofJ/ψ into γ π+ π−

The radiative decayJ/ψ → γ π⁺ π^? has been studied using the 8.6 millionJ/ψ produced in the DM2 experiment at the DCIe ⁺e^? storage rings at Orsay. The π⁺ π^? mass spectrum shows a cleanf ₂ (1270) signal, and the possible presence of two other states at thef ₂ (1720) andf ₄ (2030) masses. For thef ₂ (1270), the branching ratio BR(J/ψ →γf)xBR(f→π⁺ π^?) is measured to be (7.50±0.30±1.12)×10^?4, and the spin analysis prefers theJ=2 assignment, with helicity parametersx=0.83±0.06 andy=0.01±0.06. The existence of higher mass states is discussed.     

Subject index

We have investigated the Penning ionization of NO₂(²A₁) by He(2³S) by means of electron—ion coincidence measurements. It is possible to identify two entrance channels. The quartet state is essentially repulsive and gives rise to an electron energy spectrum similar to that found in photoionization. The doublet entrance channel is strongly attractive with a well depth D_e of 4.8 {_?0.3^+0.1 eV. Ionization out of this channel leads to very broad features in the electron energy spectrum.     

Evidence for e~+e~-→γχ_(c1,2) at center-of-mass energies from 4.009 to 4.360 GeV

Using data samples collected at center-of-mass energies of √s=4.009, 4.230, 4.260, and 4.360 Ge V with the BES detector operating at the BEPC collider, we perform a search for the process e+e-→γχc J(J =0, 1, 2)and find evidence for e+e-→γχc1 and e+e-→γχc2 with statistical significances of 3.0σ and 3.4σ, respectively. The Born cross sections σB(e+e-→γχc J), as well as their upper limits at the 90% confidence level(C.L.) are determined at each center-of-mass energy.     

Analysis of ν2, ν4 Infrared Hot Bands of SO3: Resolution of the Puzzle of the ν1 CARS Spectrum

Further analysis of the high-resolution (0.0015 cm⁻¹) infrared spectrum of ³²S¹⁶O₃ has led to the assignment of more than 3100 hot band transitions from the ν₂ and ν₄ levels to the states 2ν₂ (l=0), ν₂+ν₄ (l=±1), and 2ν₄ (l=0,±2). These levels are strongly coupled via Fermi resonance and indirect Coriolis interactions to the ν₁ levels, which are IR-inaccessible from the ground state. The unraveling of these interactions has allowed the solution of the unusual and complicated structure of the ν₁ CARS spectrum. This has been accomplished by locating over 400 hot-band transitions to levels that contain at least 10% ν₁ character. The complex CARS spectrum results from a large number of avoided energy-level crossings between these states. Accurate rovibrational constants are deduced for all the mixed states for the first time, leading to deperturbed values of 1064.924(11), 0.000 840 93(64), and 0.000 418 19(58) cm⁻¹ for ν₁, α₁^B, and α₁^C, respectively. The uncertainties in the last digits are shown in parentheses and represent two standard deviations. In addition, new values for some of the anharmonicity constants have been obtained. Highly accurate values for the equilibrium rotational constants B_e and C_e are deduced, yielding independent, nearly identical values for the SO r_e bond length of 141.734 03(13) and 141.732 54(18) pm, respectively.     

Simultaneous solution of Kompaneets equation and radiative transfer equation in the photon energy range 1-125 keV

Radiative transfer equation in plane parallel geometry and Kompaneets equation is solved simultaneously to obtain theoretical spectrum of 1-125 keV photon energy range. Diffuse radiation field are calculated using time-independent radiative transfer equation in plane parallel geometry, which is developed using discrete space theory (DST) of radiative transfer in a homogeneous medium for different optical depths. We assumed free-free emission and absorption and emission due to electron gas to be operating in the medium. The three terms n, n² and (∂n/∂x_k) where n is photon phase density and x_k=(hν/kT_e), in Kompaneets equation and those due to free-free emission are utilized to calculate the change in the photon phase density in a hot electron gas. Two types of incident radiation are considered: (1) isotropic radiation with the modified black body radiation I^MB[1] and (2) anisotropic radiation which is angle dependent. The emergent radiation at τ=0 and reflected radiation τ=τ_max are calculated by using the diffuse radiation from the medium. The emergent and reflected radiation contain the free-free emission and emission from the hot electron gas. Kompaneets equation gives the changes in photon phase densities in different types of media. Although the initial spectrum is angle dependent, the Kompaneets equation gives a spectrum which is angle independent after several Compton scattering times.