Simultaneous cw laser oscillation on transitions of Cd+ and I+ in a hollow-cathode He-CdI2 discharge

Continuous-wave laser oscillation has been obtained on four transitions of Cd⁺ and eleven transitions of I⁺ using a hollow-cathode He-CdI₂ discharge as active medium. Laser output characteristics are similar for both Cd⁺ and I⁺ transitions, and simultaneous cw oscillation has been achieved at wavelengths ranging from blue (4416 Å Cd⁺) through green $\text{(}\text{5337}\text{5378}$ Å Cd⁺, 5407 Å I⁺), yellow $\text{(}\text{5678}\text{5761}$ Å I⁺) and orange (6127 Å I⁺) to red (6585 Å I⁺).     

Cross sections for the quenching of the excited strontium state (51P1) measured in CO/N2O flames

The quantum efficiency of fluorescence, Y, of the 4607.33 Å Sr line $\text{(}{}^1\text{P}{}_1\text{?}{}^1\text{S}{}_0\text{transition}\text{)}$ was measured in four pre-mixed, laminar, shielded CO/N₂O flames of about 2700 K, with different quantitative compositions at 1 atm. From these data, the specific quenching cross sections for O₂, CO₂, CO and N₂ were found to be (152±20 Ų), (30±5 Ų), (49±8 Ų) and (16±3 Ų), respectively.     

Oscillator strengths of the first forbidden lines of rubidium

The oscillator strengths of the 5s-4d first forbidden lines of rubidium at 5165 Å were determined by performing CW tunable dye laser absorption measurements. Measured oscillator strengths of 8.06±0.48×10^-7 and 5.38±0.31×10^-7 for the ²D_{$\text{5}\text{2}$} and ²D_{$\text{3}\text{2}$} states, respectively, are compared with previously published values.     

Excitation mechanisms in CW He-Hg lasers

The collision processes responsible for populating and de-populating upper and lower levels of the cw He-Hg ion laser are investigated using flowing afterglow techniques. It is shown that the superior performance of the laser at 6150 Å compared to that at 7945 Å is not due to a difference in excitation mechanism — both are excited by charge transfer from He⁺ — but instead reflects a greater effectiveness of second kind collisions of electrons in depopulating the 7p²P_{$\text{1}\text{2}$} upper level of the 7945 Å transition. The charge transfer, excitation rate constants for several Hg II levels are compared, and values for the rate constant for the electron collision de-excitation process are deduced.     

Subpicosecond photon echoes by using nanosecond laser pulses

Subpicosecond time resolutions have been obtained in photon echoes when a sample was excited by two nanosecond dye laser pulses with a smooth and broad spectrum. The dye laser was pumped by second harmonics of a Q-switched Nd:YAG laser, and the pulse width was 10 ns. The sample was 3% Nd³⁺-doped silicate glass, and the center frequency of the dye laser was tuned at 5910 Å on resonance with the ⁴I_{$\text{9}\text{2}$} ? ²G_{$\text{7}\text{2}$}, ⁴G_{$\text{5}\text{2}$} transition of Nd³⁺. The homogeneous transverse relaxation time T₂ was measured to be 91 ps at 10 K in agreement with the previous measurements by picosecond pulses.     

Preferential excitation transfer in Cs1(6D32)- Cs(6S12) collisions

A cw dye laser beam, tuned near the Cs 8761 Å resonance (Cs¹(6P_{$\text{1}\text{2}$}) → Cs¹(6D_{$\text{3}\text{2}$}) transition) is focused into a Cs vapor. At a Cs density higher than 5 × 10¹⁵ cm^-3, we observe a greater 6P_{$\text{1}\text{2}$} population when the laser is on resonance than when it is off resonance. However, at a lower Cs density, the reverse is observed. This phenomenon is explained as due to the preferential excitation transfer process: Cs¹(6D_{$\text{3}\text{2}$}) + Cs(6S_{$\text{1}\text{2}$}) → Cs¹(6P) + Cs¹(6P), and the corresponding cross secti on is estimated to be (1.5^+1.5_-0.7) × 10^-14 cm² by fitting the experimental results to an approximate rate-equation analysis.     

Search for radiation damage in heavy ion implanted thin layer single crystal SnS22

Single crystal platelets of stannic sulfide (SnS₂, trigonal) mounted with the easy cleavage plane normal to the incident ion beam, were implanted at 100 K with 150 and 350 KeV O⁺ ions to a total dose of $\text{\$}\text{?}$2.5 × 10¹⁷ cm^?2, and subsequently examined by ¹¹⁹Sn Mossbauer spectroscopy in transmission geometry. Despite the expectation that a hot zone of $\text{\$}\text{?}$300 Å radius is created near the end of the ion track, no evidence for the thermal decomposition of SnS₂ to SnS + S is observed for thermally well clamped samples. Data for the lattice temperature of oxygen implanted SnS₂ are compared to that for unirradiated single crystal and randomly oriented powder samples.     

Investigation of the metastable state of Na2[Fe(CN)5NO] · 2H2O by optical spectroscopy. II The electronic spectra of the ground and metastable states

The absorption spectra of Na₂[Fe(CN)₅NO] · 2H₂O were measured in the visible region in the range of 3400–7000 Å. In the metastable state, an additional absorption band in the long wavelength range is observed and the transition $\text{2}\text{b}{}_{\mathrm{<mtext>2</mtext>}}\text{(d}{}_{\mathrm{xy}}\text{)→}\text{7}\text{e(π}{}^1\text{?NO}\text{)}$ becomes weaker in the excited state indicating a population of the π¹(NO)-orbital. The laser excited emission spectrum shows a broad luminescence beginning at the excitation line $\text{λ =}\text{5145}\text{A}\text{?}\text{(}\text{19,436 cm}{}^{-1}\text{)}$ with a maximum at about 6250 Å (16,000 cm^-1). A strong sharp luminescence at about 7836 Å is registered and may be assigned to a transition 3b₁(d_x²?y²) or 5a₁(d_z²) to the antibonding π¹(NO)- orbital. Further the broad luminescence is superimposed by a series of sharp spikes. These sharp spikes can also be observed for several days, when the laser is switched off, and are depending on the crystal orientation.     

Oxide thickness measurements up to 120 Å on silicon and aluminum using the chemically shifted auger spectra

Thicknesses of oxides on Si or Al can be determined up to about 120 Å using Auger electron spectroscopy, without ion-mill depth profiling, by using the ratio of the chemically shifted and unshifted peaks from the oxide and substrate, respectively. Measurement standard deviations of ± 1 Å at oxide thickness of 30 Å and spatial resolution < 10 μm are readily attainable. The absolute accuracy of the present calibration is about ± 30% at 30 Å for SiO₂. A comparison of the measured thickness d with ellipsometry revealed a disagreement which was largest at $\text{d(}\text{ellips.}\text{) = 50}\text{A}\text{?}$, where d(Auger) was 33 Å. We propose that most of this disagreement is a consequence of the finite extent of the oxide/Si interface, and the measurement of different physical parameters in the two techniques. It is demonstrated that the milling rate of SiO₂ (within about 100 Å from the SiO₂/Si interface) can be determined from ion-mill depth profiles alone and the position of the interface in the depth profile can be located within serveral Å. The electron mean free path in SiO₂ at 1615 eV was determined to be 31 ± 9 Å.     

Magnetic field dependent optical dephasing in LaF3:Er3+

Optical dephasing of the 5388 Å transition between the lowest Kramers doublets of the ⁴S_{$\text{3}\text{2}$} and ⁴I_{$\text{15}\text{2}$} multiplets of Er³⁺:LaF₃ has been studied by photon echo, optical phase switching and optical free induction decay. Er³⁺?¹⁹F hyperfine interactions produce dephasing which is two orders of magnitude faster than in previously studied non-Kramers systems, but at high field changes in the spin dynamics result in microsecond dephasing. For the lower Zeeman component of ⁴S_{$\text{3}\text{2}$}, T₂ (=6μs) is independent of H₀ whereas for the upper component the dephasing is rapid and strongly field dependent. This is quantitatively accounted for by spin lattice relaxation of the upper component of ⁴S_{$\text{3}\text{2}$}. Below 20 kG concentration and temperature dependent dephasing due to electron spin diffusion is observed.     

Displacive surface phases formed by hydrogen chemisorption on W {001}

A detailed LEED study is reported of the surface phases stabilised by hydrogen chemisorption on W {001}, over the temperature range 170 to 400 K, correlated with absolute determinations of surface coverages and sticking probabilities. The saturation coverage at 300 K is 19(± 3) × 10¹⁴ atoms cm^?2, corresponding to a surface stoichiometry of WH₂, and the initial sticking probability for both H₂ and D₂ is 0.60 ± 0.03, independent of substrate temperature down to 170 K. Over the range 170 to 300 K six coverage-dependent temperature-independent phases are identified, and the transition coverages determined. As with the clean surface $\text{(}\text{2}\text{×}\text{2}\text{)R45°}$ displacive phase, the c(2 × 2)-H phase is inhibited by the presence of steps and impurities over large distances (～20 Å), again strongly indicative of CDW-PLD mechanisms for the formation of the H-stabilised phases. These phases are significantly more temperature stable than the clean $\text{(}\text{2}\text{×}\text{2}\text{)R45°}$, the most stable being a c(2 × 2)-H split half-order phase which is formed at domain stoichiometries between WH_0.3 and WH_0.5. LEED symmetry analysis, the dependence of half-order intensity and half-width on coverage, and I-V spectra indicate that the c(2 × 2)-H phase is a different displacive structure from that determined by Debe and King for the clean $\text{(}\text{2}\text{×}\text{2}\text{)R45°}$. LEED I-V spectra are consistent with an expansion of the surface-bulk interlayer spacing from 1.48 to 1.51 Å as the hydrogen coverage increases to ～4 × 10¹⁴ atoms cm^?2. The transition from the split half-order to a streaked half-order phase is found to be correlated with changes in a range of other physical properties previously reported for this system. As the surface stoichiometry increases from WH to WH₂ a gradual transition occurs between a phase devoid of long-range order to well-ordered (1 × 1)-H. Displacive structures are proposed for the various phases formed, based on the hypothesis that at any coverage the most stable phase is determined by the gain in stability produced by a combination of chemical bonding to form a local surface complex and electron-phonon coupling to produce a periodic lattice distortion. The sequence of commensurate, incommensurate and disordered structures are consistent with the wealth of data now available for this system. Finally, a simple structural model is suggested for the peak-splitting observed in desorption spectra.     

Spin-wave scattering from A γ-Fe47Mn53alloy

Spin waves in the antiferromagnetic alloy γ-Fe_0.5Mn_0.5 have been studied at $\text{295° K(}\text{T}\text{T}{}_{\mathrm{N}}\text{= 0.63)}$ by the inelastic neutron scattering technique. We observed an isotropic dispersion and obtained a value for the spin-wave velocity of 255 ± 30 meV Å (3.88 ± 0.50 × 10⁶ cm/sec), which is the order of the spin-wave velocity in Cr (a typical itinerant antiferromagnet). The energy gap at q = 0 was found to be 7.0 ± 0.5 meV. These results suggest the existence of a long-range spin ordering in the conduction electrons of this alloy.     

Evidence of mobile correlation between conduction layers in β-alumina

The ordering of the mobile ions in the conducting layers to form an $\text{a}\text{√3 ×}\text{a}\text{√3}$ superlattice has been investigated in K⁺, Ag⁺ and Rb⁺ β-aluminas by electron diffraction. In addition to the correlation of mobile ions within the conduction layer, the correlation between conduction layers has also been detected in Rb⁺ β-alumina with periods of 68.4 Å and 22.8 Å, or three and one multiple of the $\text{c}$ dimension. A possible mechanism for such long distance correlation through spinel blocks is discussed.     

Oxalyl halides: Analysis of the 3870 Å absorption system of oxalyl chloridefluoride

Oxalyl chloridefluoride, (COCl) (COF), exhibits a very weak discrete absorption system in the region 3500–3900 Å. This system, the 3870 Å system, appears at vapor absorption pressure-paths of ～1 m atm, and merges into the much stronger 3480 Å absorption system to shorter wavelengths. The bands of the 3870 Å system have a linelike appearance under the highest resolution available, so that isotopic splittings could be used extensively as an aid to vibrational analysis. Because of the reduced symmetry of the molecule as compared to (COX)₂ species, additional vibrations are active as compared to n → π transitions of the latter; but the same type of vibrations are responsible for the band structure, namely, carbonyl stretching modes and in-plane rocking and bending modes of the two halves of the molecule. All of the stronger bands belong to one electronic transition, with origin at 25 828.7 cm^?1, which is assigned as $\text{a}\text{?}{}^3\text{A′ -}\text{X}\text{?}{}^1\text{A′}$ of the trans-molecule, produced by $\text{n → π}{}^1$ electron promotion. Only small geometric changes occur upon electronic excitation.     

The high pressure phase transitions in KF and RbF

The high pressure B1 ? B2 transitions in KF at ~ 40 kbar and RbF at ~ 30 kbar have been studied using hydrostatic X-ray diffraction. No other transitions have been observed. The addition of the $\text{ΔV}\text{V}$ for these transitions to the already existing body of literature on B1–B2 transitions in alkali halides permits an extension of Pauling's theory to larger values of radius ratios. It also permits the modified Born criterion for predicting phase transitions to be further verified. Values of ionic radii for 8 coordination we suggest are 1.33 Å for F^?, 1.84 Å for Cr^?, 2.00 Å for Br^? and 2.27 Å for I^?.     

Microwave spectral study of 2-fluorophenol: cis conformer

The microwave spectra of 2-fluorophenol and its deuterated species have been observed and analyzed in the frequency ranges 12.5–18.0 GHz (KU band) and 21.5–26.0 GHz (K band) in the ground vibrational state at room temperature. For the normal species, the radio frequency-microwave double resonance spectrum has been recorded in the frequency range 30.0–38.0 GHz. Three rotational and five quartic centrifugal distortion constants for the normal species, $\text{A}\text{?}\text{= 3337.86 ± 0.02}$, $\text{B}\text{?}\text{= 2231.92 ± 0.01}$, $\text{C}\text{?}\text{= 1337.52 ± 0.01}$, d_J = (3.5 ± 2.9) × 10^?4, d_JK = (?4.9 ± 1.5) × 10^?3, d_K = (?3.2 ± 1.0) × 10^?3, d_WJ = (?2.0 ± 1.0) × 10^?7, d_WK = (2.6 ± 0.8) × 10^?6 (in MHz), and three rotational constants for the deuterated species, $\text{A}\text{?}\text{= 3324.70 ± 0.03}$, $\text{B}\text{?}\text{= 2177.95 ± 0.03}$, $\text{C}\text{?}\text{= 1315.96 ± 0.03}$ (in MHz), have been obtained. Consideration of the r_s coordinate of the hydroxyl hydrogen atom leads to the assignment of the spectra to the cis conformer of the molecule. An r₀ structure for the cis conformer has been proposed. The nonbonded OH ? F distance is lower by about 0.3 Å than the sum of the van der Waals radii.     

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.     

The ionic distribution in Mn2+ and Zn2+ β″-alumina

The ionic distributions in Mn²⁺ and Zn²⁺ β″-alumina (idealized formula: $\text{X}{}_{\mathrm{<mtext>5</mtext><mtext>6</mtext>}}\text{Mg}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{Al}{}_{\mathrm{<mtext>31</mtext><mtext>3</mtext>}}\text{O}{}_{17}\text{;}\text{X}\text{=}\text{Mn}\text{and}\text{Zn}\text{)}$ at 296 K are reported from single-crystal X-ray diffraction studies. Mn²⁺ β″-alumina exhibits the shortest c-axis found so far in any divalent β″-alumina: 33.141(3) Å;Zn²⁺ β″-alumina, which involves the smallest divalent ion studied in the frame-work, has a considerably longer c-axis: 33.517(3) Å. Both compounds show clear evidence of short-range correlation effects in the X²⁺ ion arrangement by way of departures from the centrosymmetric space-group $\text{R}\text{3}\text{m}$ of the β″-skeleton. Both 6c end-sites and 9d mO-sites ($\text{R}\text{3}\text{m}$ notation) are occupied for both ion-types, a significantly larger occupation (60% compared to 28% of the total) lying at or near the 9d mid-oxygen sites in Mn²⁺ β″-alumina compared to Zn²⁺ β″-alumina. Disorder is also found in the column-oxygen O(5) in both cases; the O(5) displacement from the 3b site in Mn²⁺ β″-alumina (0.59 Å) is the largest found in any divalent β″-alumina. The formula-unit/cell-layer, deduced on the basis of the amounts of X²⁺ ions refined, and assuming charge compensation through Mg substitution alone, are: Mn_0.79Mg_0.57Al_10.43O₁₇ and Zn_0.87Mg_0.74Al_10.26O₁₇.     

Analysis of the B1Πu → X1Σg+ band system of 7Li2 molecule excited by the 4545- and 5287-Å visible lines of the argon ion laser

Two new fluorescence series have been excited by the two lines at the extreme ends of the range of visible Ar⁺ transitions, 4545 and 5287 Å. In each case the B¹Π_u electronic state of ⁷Li₂ is excited, to levels $\text{v′ = 12, J′ = 13 (4545}\text{A}\text{?}\text{)}$ and $\text{v′ = 2, J′ = 58 (5287}\text{A}\text{?}\text{)}$. Fluorescence to the ground state can be detected in the range 2 ≤ v″ ≤ 23 and 0 ≤ v″ ≤ 8, respectively. Measured relative intensities agree well with calculated radiative transition probabilities reported herein.     

Two-photon optically pumped laser

At high temperature, the transmission peaks of a Fabry-Perot cavity filled with rubidium show sharp structures when the frequency of the laser is close to the 5S_{$\text{1}\text{2}$} - 5D_{$\text{5}\text{2}$} two-photon transition. These structures correspond to a laser emission between 5D_{$\text{5}\text{2}$} and 5P_{$\text{3}\text{2}$}. The wavelength of this laser emission (7759 Å) is smaller than the exciting wavelength (7779 Å).