Etude spectroscopique d'un jet de plasma d'argon hors d'equilibre thermodynamique local

We have studied the properties of an argon plasmajet seeded with a few percent of hydrogen. At atmospheric pressure, significant deviations from local thermodynamic equilibrium (L.T.E.) are shown. The plasma parameters (electrondensity N_e, temperature T) have been determined from the broadening and the absolute intensity of hydrogen lines. The transition probabilities and the broadening parameters (width and shift) of some AI lines between 4000 and 6000 Å have been measured.     

Experimental transition probabilities of some Xe(I) lines

Using the light absorption technique in a ¹³²Xe afterglow plasma, we have measured the relative transition probabilities for several xenon lines which have the metastable 6s[$\text{3}\text{2}$]₂ or the resonant 6s[$\text{3}\text{2}$]₁ states as their lowest transition level. Because the transition probabilities of the 8819 Å (6p[$\text{5}\text{2}$]₃ ? 6s[$\text{3}\text{2}$]²) and 8280 Å (6p[$\text{1}\text{2}$]₀ ? 6s[$\text{3}\text{2}$]₁) lines are relatively well known, we have chosen these as reference lines and have thus been able to determine the absolute values of the transition probabilities for 19 xenon lines corresponding to transitions from 6p, 6p′, 7p, 8p, 9p, 4f and 5f to 6s[$\text{3}\text{2}$]₂, and for four lines corresponding to the transitions 6p?6s[$\text{3}\text{2}$]₁.     

Experimental stark parameters for some lines of neutral carbon,oxygen, and sulfur

Profile measurements for some multiples of neutral oxygen, carbon and sulfur have been carried out in a wall-stabilized arc. A 3.4 m Ebert spectrograph (with a dispersion of 1.1 mm/Å) adapted to simultaneous photoeletric scanning of 2 sources was used. Different gas mixtures (Ar + CO₂, Ar + SF₆, Ar + O₂) containing a small quantity of hydrogen were used for production of plasmas. Arc currents between 12 and 102 A yielded electron densities from 0.76 to 7.1 x 10¹⁶cm^-3 and temperatures between 9000 and 12,000 K. Half-widths and shifts of 7 multiplets were determined and compared with theoretical and experimental data. Good agreement was generally found except for C(I) (4771 Å), where the difference between our results and those of Nubbemeyer and Wende is too large. Stark parameters of components for the well-resolved multiplet C(I) (6) and other multiplets in the same transition arrays show the behavior expected for plasma-broadened line parameters.     

Bestimmung der absoluten Übergangswahrscheinlichkeit der Linie C II 2511 Å

The transition probability of the CII line 2511 Å has been determined from relative intensity measurements of singly ionized carbon lines calibrated by the life time value of the 4² F ⁰-level obtained by the beam-foil method. The spectra were exposed from a quasistationary pulsed discharge between carbon electrodes in a helium-hydrogen mixture. Assuming LTE Saha's equation for C III/C II yielded the plasma temperature while the electron density was determined from theH _β profile. The transition probability of the line CII 1 324 Å was evaluated by the aid of the well-known life time of the² D ⁰-level.     

Lifetimes,branching ratios and transition probabilities in molybdenum I

The radiative lifetimes of 14 excited levels in Mo I have been measured by time-resolved laser fluorescence spectroscopy. Emission branching ratios for the decay of these levels have been measured to determine absolute transition probabilities for 135 lines in the wavelength range 2600–6800Å. The transition probabilities are compared with earlier values. Erroneous J assignments in the literature are corrected.     

Transition probabilities of some lines of Ne(I)

Relative transition probabilities for twenty-four spectral lines belonging to 3p-3d transition array of neutral neon have been determined by means of emission line-intensity measurements. The lifetime of the 3d(3/2)₂ level has been measured by the delayed coincidence method obtaining a value of 20.5±2.0 ns. With this lifetime value and taking into account the 3887.1 Å forbidden line, the transition probabilities of the lines with origin in the 3d(3/2)₂ level were put on an absolute scale. The experimental values of the present work are compared with theoretical calculations obtained by use of the Coulomb approximation and intermediate coupling scheme.     

Transition probabilities of Cr(I) and Cr(II) lines lying between 422 and 485 nm,using emission measurements from a wall stabilized arc

The arc emission method has been employed to measure transition probabilities for two hundred and seventy five lines of Cr(I) (of which thirty-five are blended) and for twenty-six lines of Cr(II) lying between 422 and 484 nm. The spectra were photographed by means of a large grating spectrograph. Plasma diagnostics were carefully performed to obtain accurate values of temperatures.The absolute scale was established for Cr(I) lines using precisely known A_mn-values derived from life-time measurements for the resonance lines; for the Cr(II) lines, our absolute scale is based on accurate measurements for the line at 4242.56 Å. The smallest and largest errors estimated for the A_mn-values are ±10% and ±40%. There is generally good agreement with previous experimental data, although our values sometimes deviate by factor of 2–3 from the calculated estimates.     

Determination of transition probabilities for singly ionized vanadium

Transition probabilities of 211 spectral lines of VII, in the wavelength range 2340–4200 Å, have been determined by emission spectroscopy using a wall-stabilized arc as source. The lines studied belong to the transition arrays 3d⁴, 3d³4s-3d³4p (199 lines) and 3d³4p-3d³4d, 3d³5s (12 lines). Vanadium was introduced into the helium-arc discharge as the liquid VOCl₃. An important feature of this work is the determination of transition probabilities for many lines from a wide spectral range with a uniform absolute scale. The absolute A_ki values were obtained by normalizing relative A_ki values to an absolute scale set by ionic lifetime for the level y³H⁰₄. These results are compared with other experimental as well as theoretical results.     

Measurements of transition probabilities for doubly ionized vanadium

Transition probabilities of 43 doubly ionized V lines have been measured in the spectral range 2280–3600 Å. These lines belong to the 3d²4s–3d²4p transition array. Emission spectroscopy was used to obtain line intensities. The spectra were emitted from a He plasma with added VOCl₃ vapour in a wall-stabilized arc.     

Experimentally determined transition probabilities of the systems 6p2→6p6d, 6p7s, 6p8s of neutral lead

Branching ratio measurements have been performed for all of the observed transitions from eight levels in neutral lead (6p²→6p6d, 6p²→ 6p7s, 6p²→6p8s) excited in a hollow cathode discharge in the 200–730 nm spectral range. From the relative emission intensity data, a set of absolute transition probabilities is derived for 28 lines, including lines for which transition probabilities have not been previously published. The absolute scales are obtained by averaging the measured lifetimes of the ³P⁰_1,2, ¹P_1⁰(6p7s), ³F^0_2,3, ³D^0_1,2(6p6d) levels.     

Excitation of projectile Rydberg states in the collisions Be+-He and Mg+-He, 10–75 keV

The photoabsorption coefficient of molecular oxygen has been measured at 1215.70 Å and in the ranges 1205 Å–1214 Å and 1218 Å–1225 Å with an average resolution of ±0.015 Å. The light source in this experiment was the Doppler shifted radiation obtained from Stark quenching of a metastable hydrogen beam with energies between 2 keV and 60 keV. Using observation angles of 45°, 90°, and 135° with respect to the beam the above mentioned tuning ranges are obtained. Our data join smoothly to those of Ogawa [1] in the range 1214 Å–1218 Å and are in fair agreement with earlier measurements in other laboratories. Analytical expressions for the absorption coefficient for use in geophysical applications are presented for the whole wavelength range 1205 Å–1225 Å. Rotational structure of the absorption coefficient in the range 1220 Å–1223 Å arising from the 3-0 band of theα ¹ ∑ _u ⁺ -X ³ ∑ _g ^? forbidden transition in molecular oxygen is clearly resolved in the present measurements. A transition probability ofA=4×10⁴ s^?1 is obtained for this system. A careful study of a possible pressure dependence of the absorption coefficient was made. Except from the region were rotational line absorption occurs and the single point at 1215.70 Å no measurable effect was found for pressures below 100 Torr.     

Measurement of ultraviolet Argon(II) transition probabilities

The transition probabilities of twelve Ar(II) lines around 300nm have been measured in a stationary arc experiment at 1 atm. The reported data are based on absolute intensities, calibrated by the continuum radiation of a high temperature hydrogen plasma. For two lines the maximum emission coefficient at 26500 K has been used for an immediate determination of the respective A_mn-values. These data serve for temperature measurements at lower arc currents, where the other lines are investigated. The results, the uncertainty of which should be below ±15%, agree satisfactorily with coulomb approximation calculations, but show severe discrepancies as compared with more recent NBS tables.     

Measurement of the oscillator strengths of transitions of titanium(I) in the region 3600–4500 Å

The emission spectrum of an arc discharge stabilized by a rotating radial magnetic field, operated at high pressure in an Ar-TiCl₄ mixture, has been analyzed under the assumption that local thermodynamic equilibrium is established in the arc. The temperature distribution was determined from absolute radial emission coefficients of the 4158 Å-4200 Å Ar(I) lines.Relative transition probabilities of 52 titanium lines have been obtained in the range 3600–4500 Å and converted to an absolute scale using absolute values for the three resonance transitions at 3635, 3981 and 3998 Å.     

Identification of the SF6 transitions pumped by a CO2 laser

The quantum numbers (J values and octahedral symmetry types) of the SF₆ transitions from the ground state to v₃ = 1 that fall within ± 1.5 G Hz of the CO₂ P(14), P(18), and P(20) laser lines have been assigned. The SF₆ absorptions nearest these three laser frequencies are R(28) A⁰₂, P(33) A¹₂, and an F₂ component of P(59) or P(60), respectively.     

Low-temperature absorption contour of the ν3 band of SF6

A band contour analysis is carried out for the ν₃ absorption in SF₆. Values of ΔB = ? (1.0 ? 1.5) × 10^?4cm^?1, ζ₃ = 0.701, and ν₀ = 948.2cm^?1 are found. Tentative assignments are given for the SF₆ rotational states which are pumped by the P(14) through P(22) lines of the CO₂ laser.     

Improved separation of the rare sulfur isotopes by infrared multiphoton dissociation of SF6

The dissociation probabilities of³²SF₆ and some of³⁴SF₆ have been measured at a large number of CO₂ laser lines both at room temperature and at 140 K. The longwavelength wing of this dissociation spectrum is exponential in the wavenumber. Its logarithmic slope is proportional to the inverse temperature. Selectivities are high enough at 140 K, that the photons are consumed only for the rare isotope in the case of³⁴SF₆ and nearly so for³⁶SF₆. For³³SF₆ further improvement of the selectivity would be desirable.     

Measurement of Ar(I) and Ar(II) transition probabilities in LTE ARC plasmas

The transition probabilities of two Ar(I) lines and one Ar(II) line have been measured in emission on wall-stabilized argon arc plasmas (0·5×10⁵?p, Nm^-2?3×10⁵; 10,000?T, K?20,000; 10²²?N_e, m^-3?5×10²³) using the “method of best fit (MBF)”. The results (without line-wing correction) are for Ar(I) at 714·7 nm, A_nm=5·66×10⁵ s^-1±5%; for Ar(I) at 430·0 nm, A_nm=3·40×10⁵ s^-1±5%; for Ar(II) at 480·6 nm, A_nm=8·82×10⁷ s^-1±7%. These values were not influenced by deviations from LTE, which have been observed at electron number densities n_e?10²³ m^-3. The small uncertainties were achieved after careful corrections of different sources of error.     

Enhancement of spectral intensities of mercury triplet lines in longitudinal magnetic field

The variation of intensity of the spectral lines of the triplet series of mercury namely (7³ S ₁ → 6³ P ₀₁₂) (λ5461 Å,λ 4358 Å,λ 4047 Å) in the presence of a longitudinal magnetic field between zero and 2000 gauss has been investigated. The effect of magnetic field is found to be different as regards the variation of intensity and the occurrence of maxima in the three lines. These variations can be explained by considering the reabsorption of the spectral lines. A mathematical theory has been presented and an expression for (I _ul ) _B /I _ul has been deduced where (I _ul ) _B and (I _ul ) are the intensities of the lines with and without the magnetic field. The experimental results agree fairly well with the theoretical model.     

AgTh2(PO4)3 — A new case of the non-hydrogen bonded phosphate ferroelectric

The basic crystallographic data of AgTh₂(PO₄)₃ single crystals have been determined for the first time by means of X-ray diffraction methods. The crystals are monoclinic, space group isCc with four formula units per unit cell. The dimensions of the unit cell are:a=17·385 Å,b=6·815 Å,c=8·148 Å,β=101·10°. Using the Sawyer and Tower method it has been proved that the crystals possess ferroelectric properties. Performing the measurements at room temperature the values of spontaneous polarization and coercive field in the direction normal to (100) face have been determined.     

Relative transition probabilities of F(I) spectral lines in the visible

The relative transition probabilities of 36 neutral fluorine lines were determined by photoelectric measurements of the spectral lines emitted from a wall-stabilized arc operated in argon-fluorine mixtures. The arc current was varied from 50–70 A, the electron concentration from 1.25 to 1.55 x 10²³m^-3, and the temperature from 13,600 to 14,300 K. The assumption of LTE was used for optically thin spectral lines. The electron concentration was measured by introducing a small quantity of hydrogen, and the temperature was determined from the relative intensities of Ar lines. Close agreement was found with other experimental data obtained from arc sources.