Transitions In Na Research Articles

Hartree–Fock–Slater transition state calculations of KLL Auger energies in Na and Mg

The Hartree–Fock–Slater transition state method is used to calculate the energies for the K-L,L, KL,L2,3 and K-L2,3 L2,3 Auger transitions in Na and Mg atoms. (AIP)

Physical Properties Related to Phase Transitions in Na2CO3 Crystals

Several physical properties related to phase transitions in Na 2 CO 3 crystal were experimentally studied. Ferroelasticity was confirmed above 200°C. The temperature dependence of birefringence was measured. Pressure dependence of transition temperatures were studied above room temperature. In addition, specific heat and electric capacity in low temperature region were measured, but no distinct anomalies associated with the reported lock-in transition could be found.

Combined classical theory for excitation of alkali metal atoms by electron-impact

Combined classical theory with free-fall model for the ground state is used to calculate the direct as well as exchange excitation cross-sections for several transitions in Na, K., and Rb. The effect of attraction by the nucleus and interference effects are also discussed. In most cases, the results are found in better agreement with the available experimental results than those of the first Born approximation and binary encounter theory.

Alkali-metal resonance-line lasers based on photodissociation

We report on a series of new lasers involving transitions in Na, K, Rb, and Cs. Pulsed output powers of 1–10 kW have been obtained on the alkali-metal resonance lines. Details of the photodissociative excitation process have been studied in order to optimize these lasers.

X-ray study of phase transitions in alkali tetracyanoquinodimethanides (TCNQ)

The phase transitions in Na-, K-, and Rb-tetracyanoquinodimethanide (TCNQ) single crystals have been investigated by the x-ray critical scattering technique. The intensities of superlattice reflections, which appeared below the phase-transition temperature ${T}_{c}$, decrease with increasing temperature toward ${T}_{c}$ and the diffuse scattering intensities observed above ${T}_{c}$ increase with decreasing temperature. The intensity distribution of x-ray diffuse scattering in the momentum space shows a very strong anisotropy belonging to the ${a}^{*}$ planes, which comes from the one-dimensional crystal instability. These results are discussed in terms of the one-dimensional electron-phonon interaction.

Multiphoton ionization: mass selective laser-spectroscopy of Na 2 and K 2 in molecular beams

A cw dye laser is tuned over the B, A ← X transitions of Na 2/K 2 while a second laser or a high pressure lamp ionizes the excited states. The ions are detected by mass-spectrometry in the mixture of metal-atom clusters formed in a molecular nozzle beam. The vibronic and gyrovibronic spectra obtained show the correct intensities as compared to laser-induced fluorescence. Perturbations of certain Na 2 A ← X by the a 3Π manifold and of K 2 B ← X transitions by autoionizing levels are detected. The laser power dependence of the spectral intensities has been clarified.

A b i n i t i o calculations for the X 2Σ, A 2Π, and B 2Σ states of NaAr: Emission spectra and cross sections for fine-structure transitions in Na–Ar collisions

Configuration interaction (CI) calculations were performed for the X 2Σ, A 2Π, and B 2Σ states of NaAr. The A 2Π state is calculated to have a well depth of 492 cm−1 at an internuclear separation of 3.04 Å. Small wells of 55 and 32 cm−1 were found for the X 2Σ and B 2Σ states located at 5.01 and 6.80 Å, respectively. The spectra for A 2Π–X 2Σ emission in the limits of zero and infinite Ar pressure were calculated and compared with the experiment of York, Scheps, and Gallagher and the predictions using the pseudopotential curves of Pascale and Vandeplanque. The potentials from this work give spectra in much better agreement with experiment than the pseudopotential predictions. Total and differential cross sections for fine-structure changing transitions Na(2P1/2) +Ar→Na(2P3/2)+Ar−17.2 cm−1 were calculated by a quantum mechanical technique. The total cross sections are in excellent agreement with experimental results. The excited state differential cross sections exhibit prominent rainbow structure centered at τR=EΘR=5.5–6.0 eV deg.

The effect of linewidth on the efficiency of two-photon-pumped frequency converters

The efficiency of two-photon-pumped frequency converters as a function of the pump laser detuning and linewidth, and of the linewidth of the selected nonallowed atomic transition is studied. We show that pressure broadening of the atomic transition is a key parameter in the design of these converters. A technique is developed to measure this linewidth as a function of either self- or foreign-gas broadening using a broad-band pump laser. Measurements of the linewidth of the 3s^{2}S-3d^{2}D transition of Na, and its device implications, are presented.

The chemical and physical properties of condensed phosphates

Abstract

Beam-foil observations of Na I doubly-excited states

We identify a line at 3882.8 Å as the 3 s 3 p 4 D 7/2 − 3 s 3 d 4 F 9/2 0 transition in Na I. 2p-3s transition of Na I are observed close to the corresponding Na II resonance lines at 372 Å and 376 Å.

Oscillator strengths for neutral sodium and the interstellar sodium abundance in zeta Ophiuchi.

Use of the high-frequency deflection technique to measure radiative lifetimes for the 4p and 5p upper states in Na I, along with relative populations of a number of ns and nd states. These data have been used to obtain f-values for the corresponding resonance transitions in Na I, which proved to be in reasonable agreement with previous oscillator strengths. From the theoretical curve of growth for pure Doppler broadening, revised line ratios for D1/3303 are given and are compared with observations of Na I in zeta Oph.

Mott transitions in Na:Ar and Cu:Ar mixtures

The metal-to-nonmetal (MNM) transitions observed in Na:Ar and Cu:Ar mixtures at low temperatures have been studied by means of Mott's model for such transitions. Pseudopotential and ab initio type calculations predict critical densities which are in excellent agreement with experimental estimates. It is therefore argued that the observed MNM transitions are due to cooperative electron interaction effects, as in Mott's model. The MNM transition associated with the liquid-vapor transition of the pure metallic systems is also briefly discussed.

Infrared up-conversion with resonantly two-photon pumped metal vapors

We report efficient up-conversion of low-level ir radiation near 10 μ to the near ultraviolet. Radiation at 9.26 μ is converted to 3305 Å with a photon conversion efficiency of 58% and a corresponding power gain of 16.2. The process employs resonant two-photon pumping of the nonallowed 3s-3d transition in Na.

Experimental and theoretical studies of ferroelectric phase transitions in crystals Na(DxH1-x) (SeO3)2

Experimental data on the effect of electric fields and 7-radiation on phase transitions in Na(DxH1-X)3(SeO3)2 crystals are reported. A theoretical model which explains many of the peculiarities of these crystals is proposed.

The enthalpy of sodium oxide Na 2O to 1300 K by drop calorimetry

A high-precision drop-calorimetric system has been used to measure the enthalpy (relative to 298.15 K) of Na 2 O in the temperature range 500 to 1300 K. A rapid rise in the derived C p ( T ) is observed about 900 K, which may be attributed to the onset of a diffuse transition in Na 2 O and a disordering of the Na + ions. The results are therefore represented by two equations, one for temperatures below 900 K and another for temperatures above 900 K. In the range 298 to 900 K: { H o ( T ) − H o ( 298.15 K ) } / c a l t h m o l − 1 = 13.8814 ( T / K ) + 4.4249 × 10 − 3 ( T / K ) 2 − 4532.09. In the range 900 to 1300 K: { H o ( T ) − H o ( 298.15 K ) } / c a l t h m o l − 1 = 35.4157 ( T / K ) − 2.80046 × 10 − 2 ( T / K ) 2 + + 1.42549 × 10 − 5 ( T / K ) 3 − 8036.87. All temperatures are based on IPTS-68. Values of { H o ( T )− H o (298.15 K)}, C o p ( T ), { S o ( T ) − S o (298.15 K)}, Δ H o f ( T ), Δ G o f ( T ), and log K o p ( T ) are tabulated.

Raman and Infrared Spectra of Na2SeO3, NaHSeO3, H2SeO3, and NaH3(SeO3)2

The Raman and infrared spectra of four selenite compounds have been measured and compared to the Raman spectra of SeO32−, HSeO3−, and H2SeO3 in solution obtained previously by Walrafen. A. general force field has been used to obtain force constants for the selenite ions and to examine the effect of varying the stretching force constants. The results are discussed in relation to phase transitions in Na(H1−xDx)3(SeO3)2 which have been associated with ordering of the hydrogen atoms.

Raman study of the phase transitions in Na(H1-xDx)3(SeO3)2

The solid phases of Na(H1 - xDx)3(SeO3)2 were studied using Raman scattering. Samples with x = 0, 0.1, 0.3 and 0.75 were examined between room temperature and -185°C. Spectra were recorded over the 30 to 900 cm-1 range. The results suggest that the hydrogen atoms are disordered in phase I and ordered in phases III, III', and III''. The lack of splitting of the v4' mode of the SeO32- ion in phase II suggests that phase II is less ordered than phases III and III'. Other changes in split tings from phase to phase are consistent with changes in crystal symmetry. The results do not reflect strong changes in the strength of the hydrogen bonds with change of phase.

Electric Quadrupole Transitions in Na I, Mg II and Al III

Theoretical multiplet strengths for electric quadrupole transitions between 2S, 2P0, 2D, and 2F0 levels of Na I, Mg II, and Al III have been calculated using Hartree–Fock wave functions of frozen-core type. The resulting 2S–2D oscillator strengths for Na I are in good agreement with calculations by Bogaard and Orr, Boyle and Murray, and Warner; however, for Mg II there is a discrepancy of a factor of 2 between our results and those of Warner.

Electronic Excitation in Fast Collisions of Na with SO2 and NO2

A sputtered Na beam has been used to investigate collisionally induced electronic excitation in scattering with SO2 and NO2. Light from the radiative decay of excited electronic states was observed at several wavelengths, and measurements were made of the excitation cross sections as a function of the center-of-mass collision energy in the range 1–30 eV. In both scattering systems, the most intense light measured originated from the Na (32P→32S) D line. Light from the (42D→32P) Na transition was observed, but its intensity was more than an order of magnitude smaller than that of the D line. Emission also occurred from transitions with long radiative lifetimes (∼40 μsec). This emission is probably due to the B1→A1 molecular transitions of SO2 and NO2. The results have been discussed in terms of a potential curve-crossing mechanism which seems to satisfactorily explain collisionally induced alkali atom excitation. For the molecular emission, an alternate mechanism has also been considered which involves vibrational coupling of the A1 and B1 states.

Beam-Foil Spectroscopy of Sodium between 0.5 and 2 MeV

The optical excitation of a beam of ${\mathrm{Na}}^{+}$ ions by a thin carbon foil has been observed in the spectral range 1100-6000 \AA{}. Ions with a charge state as high as ${5}^{+}$ were present in the beam after the foil. A large number of untabulated lines has been detected and several identifications are proposed mainly in the Na IV and Na V spectra. The decay along the beam of numerous transitions in Na II and Na III has also been recorded. In a few favorable cases, the resolution of the decay curve gives a useful estimate of the mean life of the corresponding excited state.