Forbidden Components Research Articles

Calculation of helium plasma satellites in turbulent plasmas

Neutral helium line profiles (2 P-4 D), under the influence of suprathermal electric field fluctuations, are calculated with the use of a relaxation line-broadening theory. First-order plasma satellites at the nearby forbidden component (2 P-4 F) are investigated for various turbulent plasma conditions. The spectral energy densities of the suprathermal electric field fluctuations are analytically modeled to infer quantitative relations between the plasma satellites and the enhanced electric field. It is found that the far satellite can grow stronger than the near satellite and both satellites will split into doublets as the turbulent electric field increases. The theory is generalized to higher order to describe the second harmonic plasma satellites near the allowed transition.

Electric dipole moment of 3He

Abstract The contribution of CP violating nucleon-nucleon interaction to the electric dipole moment of 3 He is evaluated following a recent proposal for its experimental detection. Two models of CP violating interactions are used, namely, the Kobayashi-Maskawa mechanism and the occurrence of the θ term in the QCD lagrangian. These CP violating interactions are combined with realistic strong nucleon-nucleon interactions to induce a CP forbidden component of the 3 He wave function. The matrix element of the electric dipole operator is then evaluated between CP allowed and CP forbidden components yielding the observable electric dipole moment. Using the parameters emerging from the penguin terms in the Kobayashi-Maskawa model we obtain a result much larger than the electric dipole moment of the neutron in the same model. On the other hand, no enhancement is found for the θ-term mechanism. A possible explanation for this difference is discussed. Numerical estimates can be given only in the Kobayashi-Maskawa model, giving d( 3 He ) ≈ 10 −30 e · cm . In the second mechanism, the estimate gives d( 3 He ) ≈ 10 −16 θ .

Dispersive plasma-satellites of a dipole-forbidden transition and the rotating field model

A clear distinction is made between (a) the coupled transitions of optical photons and transverse plasmons in microwave experiments and (b) the dispersive plasma-satellites in a cable-pulsed, double-cathode glow discharge. The former involve a radiation-damped dipole interaction and are not necessarily accompanied by a central component. The latter conserve the sum of the angular momentum projections of spin-one plasmons and atoms in the sense that the ensemble-averaged electron-induced absorption probability at the position of the forbidden component is split into three components, separated by the plasma frequency ω p . The far and near σ-satellites change the projection quantum number by one unit, while the central π-component does not, because of rotationally transforming the Schrödinger equation at angular velocities of ±ω p in the atomic ( x, y)-plane. The theory is compared with measured optical spectra.

Particle-hole interacting boson approximation applied toNi56

The particle-hole interacting boson approximation proposed by Feshbach and Iachello is applied to the low-lying excited states of $^{56}\mathrm{Ni}$. Since the particle-hole interaction seems to be dominant in the low-lying excited states in $^{56}\mathrm{Ni}$, the particle-hole pairs are taken as the bosons. The rest of the Hamiltonian is considered as the interactions between the bosons. The first excited ${2}_{1}^{+}$ and ${4}_{1}^{+}$ states as well as the ground state are reasonably described without introducing any artificial treatments into the calculation. The first excited ${0}_{1}^{+}$ state is shown to be the two-boson dominant state which is consistent with the experimental prediction. The forbidden components for a fermion system inherent in the boson wave function are investigated. As the result, the wave functions of the ${0}_{g}^{+}$, ${2}_{1}^{+}$, and ${4}_{1}^{+}$ states are shown to be almost free of mixing of the components.

Stark broadening of the He I 4471-A

We have measured the profile of the He i 4471-A\r{} line and its forbidden component at 4470 A\r{} in the plasma of a high-pressure pulsed discharge at an electron temperature of about 1.5 eV, and at electron densities ranging from 0.5\ifmmode\times\else\texttimes\fi{}${10}^{17}$ to 2.0\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$. Contrary to all preceding experiments performed at higher electron temperatures, in the present experiment better agreement with theoretical calculations is found. A tentative explanation of this improved agreement is offered.

Production of dense, cool plasmas by resonance pumping of sodium vapor.

High-electron-density, low-temperature plasmas have been produced with a minimum of 1 electron per Debye sphere by high-power, short-pulse resonant laser pumping of dense (${10}^{16}$--4\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$) sodium vapor. The recombining plasmas were diagnosed by time-resolved emission spectroscopy. Electron densities between 0.5\ifmmode\times\else\texttimes\fi{}${10}^{16}$ and 2.2\ifmmode\times\else\texttimes\fi{}${10}^{16}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ were inferred from widths and shifts of allowed lines and intensities of forbidden components. Electron temperatures between 0.2 and 0.3 eV were calculated from relative line intensities, since all states above 3d were shown to be in partial local thermodynamic equilibrium. Such low temperatures coupled with other experimental evidence suggested that laser-induced associative ionization involving atoms in the 3p state was the dominant ionization mechanism.

Threshold spectrum of CO2

A high-resolution threshold electron impact spectrometer is used to obtain a threshold spectrum of CO2 in the energy range from 3 to 20 eV. The dominant feature of the spectrum is the strong excitation of the unoccupied 2 pi u valence orbital from both 1 pi g and other deeper lying filled orbitals, giving rise to strong overlapping continua. A new, long vibrational progression in the bending mode is found, between 10 and 11 eV. The most prominent Rydberg series start above 12 eV and are associated with optically forbidden components of the transition to nd orbitals, not detected previously. Isoenergetic decay of the 2 Pi u resonance, populating the ground-state vibrational levels, is observed with an intensity comparable with the strongest electronic transitions. Strong resonant near-threshold excitation is found at 11.02 eV.

Variation of the ion dynamics parameter in stark-broadened helium lines

Stark broadening of quasidegenerate He lines at λ = 447 nm and 492 nm hasbeen investigated at low electron densities ( N e = 10 21 and 3 x 10 21 m -3). The perturber mass was varied by using H +, He + and Ar + ions. Variation of the parameter ( T 0 /μ) 1/2 by a factor of 3 is accompanied by marked ion-dynamical effects in the forbidden component. The results are compared with calculations according to the unified theory and the model microfield method. Characteristic deviations are observed and critically discussed.

Magnetically induced luminescence of [Ir(2=phos) 2]ClO 4

The intense luminescence of [Ir(2=phos) 2]ClO 4[2=phos is cis-1,2-bis(diphenylphosphino)ethylene] in a rigid glass matrix at 9.5 K was monitored while external magnetic field ( B max = 6.7 T) were applied. Radiative coupling to the ground state from a forbidden component was induced by the field.

The 275-nm absorption system of anisole

The 275-nm absorption systems of anisole (methoxybenzene) and three deuterated derivatives have been photographed at medium to high resolution. The origin bands lie at 36 386.4, 36 389.6, 36 557.2, and 36 560.4 cm −1 for C 6H 5OCH 3, C 6H 5OCD 3, C 6D 5OCH 3, and C 6D 5OCD 3. The vibrational structure, which was analyzed in some detail, was found to be very similar to that of the analogous system of phenol. The spectrum consists of both allowed and forbidden components although the forbidden component, principally evident through activity of vibrations 18 b and 6 b, is relatively weak.

Analysis of vibronic intensities in the phosphorescence spectrum of dimethylbenzaldehydes in durene

An attempt is reported to explain the main intensity patterns in the phosphorescence spectra of 2,4-, 2,5- and 3,4-dimethyl-benzaldehyde-1 h 1 and -1 d 1, observed previously. The analysis is based on CNDO and MINDO calculations of (transition) dipole moments, spin-orbit couplings, vibronic couplings, state energies, normal coordinates and vibrational frequencies. Where possible these quantities are empirically checked and corrected. Additional information, especially about the separation of the closely spaced T 1( 3ππ *) and T 2( 3nπ *) states, is obtained from phosphorescence excitation spectra reported here for all six isomers. The phosphorescence spectra consist of two components, an “allowed” component of 3ππ * and a “forbidden” component of 3nπ * symmetry. It is concluded that the allowed component is partly induced by the crystal field. The forbidden component is vibronically induced by out-of-plane vibrations among which the aldehydic CH(CD)-wag mode is the most active. The observed intensity patterns for this component are ascribed to interference between two mechanisms, one involving vibronic coupling between S 0 and S 1( 1nπ *) and spin-orbit coupling between S 1 and T 1, the other involving vibronic coupling between T 1 and T 2 and spin-orbit coupling between S 0 and T 2. Within the groups of either 1 h 1 or 1 d 1 isomers, the main changes in the spectrum are shown to be due to the change in T 1–T 2 energy separation. The changes observed upon deuterium substitution in the aldehyde group involve, in addition to changes in the T 1–T 2 gap, changes in vibronic coupling due to normal-coordinate mixing. All these spectral changes are reproduced by calculations based on a mixture of theoretical and empirical input parameters, derived from, or at least consistent with, other observations, including excitation spectra, dipole moments and zero-field splittings. It is concluded that the mechanisms underlying these calculations offer a satisfactory explanation of the observed intensity patterns in the phosphorescence spectra of dimethylbenzaldehydes.

An evaluation of the possibility of studying flare plasma turbulence using the satellites of Hei line forbidden components

Using the Baranger-Mozer method, we explore the possibility of diagnosing the flare plasma of forbidden Hei lines, that permits the determination of the plasma oscillation frequency and noise level. Examination of the Hei lines observed in solar flare has led us to conclude that: In the spectrum of the solar flare of 26 September, 1963 we detected satellites of the forbidden component of the 3820 A line and used its relative intensity to derive the level of low-frequency oscillations (∼1.5 kVcm-1).

Site dependence of the 1 1A g to 2 1A g transition of all-trans-1,3,5,7-octatetraene

Highly resolved emission and one-photon fluorescence excitation spectra and fluorescence lifetimes for all-trans-1,3,5,7-octatetraene substituted in a series of n-alkane crystals maintained at liquid helium temperatures have been measured. In the n-octane host, the 1 1Ag to 2 1Ag transition is strictly symmetry forbidden: In other hosts, the spectra exhibit both allowed and symmetry forbidden components. While the relative intensity of the allowed (built on the 0–0) and the symmetry forbidden (built on odd symmetry vibrational modes) components of the spectra are sensitive to local perturbations, the energies of the excited 1 1Ag and 1 1Bu states and the vibrational development of the 1 1Ag to 2 1Ag transition are nearly the same in all of the hosts studied. The increase in the allowed component of the spectrum with increasing site perturbation correlates with a decrease in the measured fluorescence lifetime.

Temporally and spatially resolved plasma satellites in a hollow-cathode source

Observations of the temporal dependence of plasma satellites to the forbidden component of He I 447 nm in a hollow-cathode source show, firstly, that the satellite intensities can exceed the forbidden component intensity and secondly, that, for a brief period, the near-satellite intensity increases by the same amount as the far-satellite intensity decreases. A splitting of the forbidden component was observed when the frequency separation of the satellites and forbidden component reached half the value of the separation between the allowed and forbidden components. The satellite frequencies observed along the symmetry axis in the negative glow as well as in the dark spaces (below spiking threshold) are constant.

Experimental Study of Ion Dynamic Effects in Overlapping Helium Lines at Low Densities

Abstract The line profiles of the overlapping helium lines 447.1 nm and 492.2 nm have been investigated in an improved plasma source of high purity at electron densities of 1 × 1021 m−3 and 3 × 1021 m−3 . The plasma parameters Ne, Te and T0 were determined carefully by independent diagnostics, which enables a critical comparison with existing theories (BCS II and MMM). We observed ion dynamic effects which considerably modify the line shape of the forbidden components. Our experiments extend the existing observations towards higher ion temperatures. Systematic trends observed earlier are critically discussed.

Rotational analysis of the 2 01 and 2 11 bands in the à 2Σ +-X̃ 2Π spectrum of N 2O +

Analysis of new emission spectra of à 2Σ +-X̃ 2Π in N 2O +, including the forbidden components with Δν 2 = 1, have made it possible to locate all four vibronic components of the ν″ 2 = 1 manifold. Principal rotational constants and spinvibronic terms are given. A previous estimate of the Renner parameter is revised to a value of −0.179 ± 0.002.

Anomalous heat conduction at the ends of a theta pinch

In a small theta pinch, a density pulse propagating to the end is found to form after the compression phase. Doppler-shift measurements of the He ii, λ = 4686 Å line indicate that axial particle flow is present only during the implosion, thermal conduction being the dominant end-loss mechanism at later times. Comparison of the actual heat flux with that expected from classical theory, the presence of an enhanced forbidden component as well as plasma satellites of the He i, λ = 4922 Å line outside the coil region, and a flat-top electron distribution function obtained by Thomson scattering, lead to the conclusion that thermal conduction is anomalous. The concept of a replacement wave is successfully applied to account for the observed phenomena.

Hei Lambda 4922 IN B-Stars - Comparison of Theory and Observations

Profiles of the He I λ4922 line have been observed in 15 B-type stars with an unintensified Reticon detector on the coudé spectrograph of the University of Hawaii's 2.2 m telescope on Mauna Kea. The observations are compared with the theoretical line profiles computed by Mihalas, Barnard, Cooper, and Smith, who used an improved line broadening theory. The results show that the computed profiles reproduce the core and red wing of the stellar profiles, but the forbidden component in the blue wing of the line is deeper and broader than the theoretical predictions. Photographic Hα line profiles have been obtained for three of our program stars, and for this sample we find that the Balmer line, He I λ4922, and Strömgren photometric colors yield a consistent set of atmospheric parameters.

Study of ion dynamic effects at low electron densities on the lines He I 447.1 and 492.2 nm

The effects of ion motion on the Stark profiles of the lines He I 447.15 nm (2 3P-4 3D) and its forbidden component He I 447.0 nm (2 3P-4 3F) has been studied in a plasma jet for electron densities between 0.8 × 10 21 and 4 × 10 21 m -3. The ion velocity was changed by using perturbing ions of different masses. An important smearing of the central part of the line was observed, and there was some evidence of an extra-broadening of the line when the ion velocity increased. A comparison of our results with the recent Model Microfield Method calculations shows an improved agreement in the line profile description relatively to previous calculations. A confirmation of these measurements was given by the study of the ion motion effect on the profile of the line He I 492.19 nm (2 1P-4 1D) and its forbidden component He I 492.03 nm (2 1P-4 1F).

Comments on "Spectroscopic investigation of plasma turbulence"

Recently Al-Shiraida, Hirose, and Skarsgard ( I ) helium as shown in Fig. 1. The helium spectrum have presented measurements of plasma satellites was obtained from an ~f-discharge run in a tube that near the helium line at 492.2 nm in a toroidal exhad previously been contaminated with small periment. These structures in the line profile are amounts of hydrogen. Comparing our measureinterpreted as being due to highand low-frequency ments with those of ref. 1 and a theoretical line electric fields originating from plasma turbulence. profile of the 492.2 nm line (4) at tz, = 5 x I O l 9 m-' However, spectroscopic measurements of and T, = 40000 K , we come to the following conplasma satellites are always difficult because of clusions: possible misinterpretation of structures stemming (I) The measured (1) halfwidth of the allowed line from molecular impurities, as has been shown both is much narrower than the theoretical profile prefor the helium line at 447.1 nm (2) and for the hydicted at the independently recorded density, indidrogen Hpline (3). cating that the spectrum is emitted from wall reWe have also measured the 492.2 nm line of gions ofthe plasma. (2) There is a rather large amount of background radiation around the allowed line compared to the theoretical prediction. From our measurements it is evident that this quasicontinuum probably stems from molecular bands of hydrogen. (3) The observed features are narrower than the minimum width predicted for high-frequency plasma satellites, which is given by the width of the allowed line. (4) In comparison with our measurements one can see that the structures of the profile in ref. 1 not only coincide on the blue wing near the forbidden component but also on the red wing with hydrogen molecular lines. In conclusion we suggest that the fine structures measured by Al-Shiraida et al. (1) are not due to two-photon transitions but probably due to hydrogen molecular lines. These lines could originate in the wall region of the discharge. which is usually contaminated.