Diode laser measurements of strengths,half-widths,and temperature dependence of half-widths for CO2 spectral lines near 4.2 μm

Absolute line strengths have been measured at room temperature for spectral lines in the R branch of the ν₃ band of ¹²C¹⁶O₂, ¹²C¹⁶O¹⁸O, and ¹²C¹⁶O¹⁷O and the (ν₂ + ν₃) ? ν₂ and (ν₁ + ν₃) ? ν₁ bands of ¹²C¹⁶O₂ in the region 2365–2393 cm^?1 using a tunable diode laser spectrometer; from these measurements band strengths have been computed. Self- and nitrogen-broadened half-widths have been measured for some ν₃ lines of ¹²C¹⁶O₂ and ¹²C¹⁶O¹⁷O, and nitrogen-broadened half-widths measured for some (ν₂ + ν₃) ? ν₂ band lines of ¹²C¹⁶O₂. From measurements made over a temperature range from 217 to 299 K we have obtained temperature coefficients n, for the N₂-broadened Lorentz half-width defined as $\text{b}{}_{\mathrm{L}}{}^0\text{(T) = b}{}_{\mathrm{L}}{}^0\text{(T}{}_0\text{)(}\text{T}\text{T}{}_0\text{)}{}^{\mathrm{?n}}$, for the ν₃ and (ν₂ + ν₃) ? ν₂ bands of ¹²C¹⁶O₂. They are 0.757 ± 0.008 and 0.789 ± 0.015, respectively.     

Intensities and pressure-broadened widths of CO2 R-branch lines at 15 μm from tunable laser measurements

Intensities and half-widths of individual lines, over the temperature range 200–325°K in the 15 μm bands of ¹²C¹⁶O₂, have been determined with a tunable diode laser spectrometer. Measurements were made on pure CO₂ and on dilute CO₂-in-N₂ mixtures on the R-branches of the 01¹0-00⁰0 and 02²0-01¹0 transitions. Intensities are approximately equal to those listed in the AFGL compilation. The pressure-broadened half-widths follow the general relationship $\text{b}{}_{\mathrm{L}}{}^0\text{(T) = b}{}_{\mathrm{L}}{}^0\text{(T}{}_0\text{) [}\text{T}{}_0\text{T}\text{]}{}^{\mathrm{n}}$ where n varies considerably from line to line but is always greater than $\text{1}\text{2}$.     

Strengths and lorentz broadening coefficients for spectral lines in the ν3 and ν2 + ν4 bands of 12CH4 and 13CH4

Line strengths and self- and nitrogen-broadened half-widths were measured for spectral lines in the ν₃ and ν₂ + ν₄ bands of ¹²CH₄ and ¹³CH₄ from 2870–2883 cm^?1 using a tunable diode laser spectrometer. From measurements made over a temperature range from 215 to 297 K, on samples of ¹²CH₄ broadened with N₂, we deduced that the average temperature coefficients n, defined as $\text{b}{}_{\mathrm{<mtext>L</mtext>}}{}^0\text{(T) = b}{}_{\mathrm{<mtext>L</mtext>}}{}^0\text{(T}{}_0\text{)(}\text{T}\text{T}{}_0\text{)}{}^{\mathrm{?n}}$, of the Lorentz broadening coefficients for the ν₃ and ν₂ + ν₄ bands of ¹²CH₄ were 0.97 ± 0.03 and 0.89 ± 0.04, respectively. A smaller increase is observed in line half-width with increasing pressure for E-species lines, for both self- and nitrogen-broadening, than for other symmetry species lines over the range of pressures measured, 70 to 100 Torr.     

Polarization spectroscopy of the E0g+-B0u+ band system of Br2

The E-B (0_g⁺-0_u⁺) band system of Br₂ has been investigated at Doppler-limited resolution using polarization labeling spectroscopy. Merged E state data for the three naturally occurring isotopes in the range v_E = 0–16, expressed in terms of the constants for ⁷⁹Br₂, are (in cm^?1) Y_0,0 = 49 777.962(54), Y_1,0 = 150.834(22), Y_2,0 = ?0.4182(28), Y_3,0 = 6.6(11) × 10^?4, Y_0,1 = 4.1876(28) × 10^?2, Y_1,1 = ?1.607(16) × 10^?4, and Y_0,2 = 1.39(39) × 10^?8. The bond distance is $\text{r}{}_{\mathrm{<mtext>e</mtext>}}\text{= 3.194}\text{A}\text{?}$, and the diabatic dissociation energy to $\text{Br}{}^{\mathrm{+}}\text{(}{}^3\text{P}{}_2\text{) +}\text{Br}{}^{\mathrm{?}}\text{(}{}^1\text{S}{}_0\text{)}\text{is 34 700 cm}{}^{\mathrm{?1}}$.     

Electrical conductivity of the system Y2O3CeO2

The electrical conductivity of the system Y₂O₃CeO₂ was measured in the temperature range 500–1100°C and P_o2 range 10^–7?10^?1 atm. Possible defect models were suggested on the basis of conductivity data, which were investigated as a function of temperature and of P_o2. The observed activation energies were 0.40 eV and 1.79 eV in the low- and high-temperature regions, respectively. The observed conductivity dependences on P_o2 were in the temperature range 500–750°C and at temperatures from 750–1100°C. It is suggested that the system Y₂O₃CeO₂ shows a mixed ionic plus hole conduction due to an O^″_i defect and an electronic hole conduction due to a V^'''_Y defect in the low- and high-temperature regions, respectively.     

Laser emission spectrum and tuning of the HgCl visible laser

The laser emission spectrum of the pulsed mercury halide HgCl laser excited in a UV preionised transverse discharge has been investigated. Simultaneous oscillation on many vibrational-rotational lines of the transition has been observed from 533.4 to 565.8 nm. Emission lines from the upper B state are assigned to vibrational level v′ = 0 to 12 and to vibrational levels of the lower X state of υ″ = 18 to 32. A new broadband low gain laser emission overlapping the B-X line emission has been observed. Laser performance has been measured over a wide range of excitation and laser gas conditions; an overall efficiency > 0.2% and a volumetric efficiency of 0.75 Jλ^-1 has been obtained. Tuning characteristics of the laser emission over the range of oscillation frequencies are reported.     

Oxygen and carbon monoxide isotope exchange reactions on rhenium

The catalytic efficiency, E, of rhenium at high temperatures for the equilibration of a mixture of carbon monoxide isotopes (¹²C¹⁸O + ¹³C¹⁶O) is reduced by pre-adsorbed oxygen; E at 1300 K declines linearly to zero at an oxygen uptake of about 5 × 10¹⁴ atoms cm^?2. The replacement of one pre-adsorbed carbon monoxide isotope by another can be correlated with the characteristic desorption temperatures of the two main states (α and β) of CO on Re. The observation that a considerable fraction of CO is non-replaceable at filament temperatures below 700 K suggests a high activation energy for migration of some adsorbed CO. The probability of exchange of ¹⁶O between an oxygenated rhenium filament and gaseous ¹²C¹⁸O for oxygen coverages ?4 × 10¹⁴ O atoms cm^?2 is 0.012 per 10¹⁴ O atoms cm^?2 per collision with the filament at 900 K. The surface reaction $\text{Re-}{}^{16}\text{O +}{}^{12}\text{C}{}^{18}\text{O}{}_{\mathrm{(g)}}\text{= Re-}{}^{18}\text{O +}{}^{12}\text{C}{}^{16}\text{O}{}_{\mathrm{(g)}}$ is completely reversible. However, in the presence of nitrous oxide no reaction is observed until the filament temperature exceeds 1600 K, when continuous decomposition of N₂O is appreciable. Possible transition states for isotope exchange are discussed.     

Infrared bands of 12C2HD

The rotational structure of about 40 bands of ¹²C₂HD observed in the region 6000?600 cm^?1 has been measured and interpreted with the purpose of determining a comprehensive set of molecular constants for this isotopic variety of acetylene. Combining these data with the results for ¹²C₂H₂ and ¹²C₂D₂, a reevaluation of the equilibrium internuclear distances for the acetylene molecule has been made: $\text{r}{}_{\mathrm{e}}\text{(CH) = 1.06215 ± 17 × 10}{}^{\mathrm{?5}}\text{A}\text{?}$ and $\text{r}{}_{\mathrm{e}}\text{(CC) = 1.20257 ± 9 × 10}{}^{\mathrm{?5}}\text{A}\text{?}$ were obtained. This paper presents all the molecular constants derived in this study.     

3Σu−-3Σu+ coupling in the O2B3Σu− predissociation

The role of $\text{B}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{-2}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ spin-orbit mixing in the O₂ Schumann-Runge predissociation is investigated. The $\text{2}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ state is found to cross the $\text{B}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}$ state near 2.0 Å with an interaction matrix element of approximately 55 cm^?1. This state contributes to the widths of the Bv ≥ 6 levels, but introduces only small level shift perturbations. When the partial widths due to the ${}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{-}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ interaction are added to the previously calculated widths due to the ⁵Π_u, ³Π_u, and ¹Π_u states, reasonable agreement is obtained with experimental measurements on O¹⁶O¹⁶ and O¹⁸O¹⁸. The possibility of non-Lorentzian line profiles and the dependence of the width on rotational quantum number is investigated. The approximation of the spin-orbit matrix element by its value at the crossing point is shown to be a good approximation for calculating the second difference perturbations.     

Band contour analysis of compounds with pure isotopes: The E fundamentals of HC35Cl3

The vibration-rotation transitions for v = 1 ← 0 of NO (${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$) have been studied by using the technique of laser magnetic resonance spectroscopy. Five magnetic resonance lines are observed with three CO laser lines in the range from 1859 to 1886 cm^?1. From these, three zero-field transition frequencies, v = 1 ← 0; $\text{R(}\text{3}\text{2}\text{)}$, $\text{P(}\text{7}\text{2}\text{)}$, and $\text{P(}\text{9}\text{2}\text{)}$ are obtained with an accuracy of ±0.0007 cm^?1. The molecular constants which have been determined by borrowing centrifugal constants from a previous infrared work are $\text{B}{}_{02}{}^1\text{= 1.72004 ± 0.00006}\text{cm}{}^{\mathrm{?1}}$, $\text{B}{}_{12}{}^1\text{= 1.70212 ± 0.00010}\text{cm}{}^{\mathrm{?1}}$, and $\text{G(v = 1) ? G(v = 0) (}\text{for}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{) = 1875.8470 ± 0.0007}\text{cm}{}^{\mathrm{?1}}$.     

Laser magnetic resonance spectrum of BrO (2Π12 ← 2Π32)

Magnetic dipole transitions between the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and ${}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ components of the ground electronic state of BrO have been detected using the technique of laser magnetic resonance on three CO₂ laser lines between 964 and 970 cm^?1. This is the first direct observation of the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ state in BrO. The spin-orbit splitting parameter, A, is determined to be ?967.9831(2) cm^?1 for ⁷⁹Br¹⁶O and ?967.9981(2) cm^?1 for ⁸¹Br¹⁶O. Accurate values for the rotational constant $\text{B}{}^{\mathrm{<mtext>eff</mtext>}}\text{(}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}$, the hyperfine parameters ($\text{b}{}_{\mathrm{F}}\text{+}\text{2c}\text{3}$) and d, the Λ-doubling parameter p, and the Zeeman parameter g| are also determined from an analysis of the measured spectra.     

The E-B band system of diatomic iodine

Sequential pump and probe pulses are used to excite state-selected E ← B ← X transitions in I₂ vapor, and the E ← B bands recorded by polarization-labeling spectroscopy at relatively high dispersion. Molecular constants and Dunham expansion coefficients Y_n,0 (n = 0–7), Y_n,1 (n = 0–3), and Y_n,2 (n = 0, 1) for the E state are obtained in the range 0 ≤ v_E ≤ 96, based on a global least-squares fit of 1050 assigned rotational transitions. Definite evidence is cited to show that the EO_g⁺ ion-pair state correlates diabatically with the ground state $\text{I}{}^{\mathrm{?}}\text{(}{}^1\text{S}{}_0\text{) + I}{}^{\mathrm{+}}\text{(}{}^3\text{P}{}_2\text{)}$ of the separated ions.     

Diode laser spectroscopy of the CCl radical

Vibration-rotation transitions of the fundamental band have been observed for both C³⁵Cl and C³⁷Cl in the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and ${}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ states by using an infrared diode laser spectrometer with Zeeman modulation. A few lines of the “hot” band (v = 2 ← 1) have also been recorded for C³⁵Cl. From an analysis of the observed spectra improved values were obtained for the vibrational harmonic frequency and anharmonicity constant, rotational constants, and Λ-doubling parameters. It was found necessary to take into account centrifugal distortion effects on the spin-orbit coupling constant A in the analysis, which gave $\text{(}\text{dA}\text{dr}\text{)}{}_{\mathrm{<mtext>e</mtext>}}\text{r}{}_{\mathrm{<mtext>e</mtext>}}$ to be ?176 ± 38 or ?125 ± 38 cm^?1, depending upon whether ²Σ^? or ²Σ⁺ states contribute more to the Λ-type doubling. The equilibrium internuclear distance r_e was calculated from the derived rotational constants to be 1.64506 ± 0.00016 Å.     

The B̃2Σ−g (Πu) ← X̃2A1 system of nitrogen dioxide in neon matrices

The $\text{B}\text{?}\text{←}\text{X}\text{?}$ band system of NO₂, ${}^2\text{Σ}{}^{\mathrm{?}}{}_{\mathrm{g}}\text{(π}{}_{\mathrm{u}}\text{) ←}{}^2\text{A}{}_1$, has been measured in absorption in a neon matrix at 6 K, using ¹⁵NO₂ and N¹⁸O₂ in addition to the normal isotope. The spectrum consists essentially of a single, long progression of bands terminating on successive levels of the bending mode in the upper state. Transitions to odd- and even-v₂′ states occur with a uniform intensity distribution indicating that the rotation of the bent ground state of NO₂ about its near-prolate axis is hindered in the matrix. The observations strongly suggest that the top axis of the molecule coincides with a C₂ axis of neon crystals in the polycrystalline matrix. Relative to the vapor absorption the matrix spectrum is red shifted by about 150 cm^?1, the crystal field parameter V₂ and principal constants of the $\text{B}\text{?}$ state of ¹⁴N¹⁶O₂ in neon being

$\text{T}{}_{010}\text{14 571 cm}{}^{\mathrm{?1}}\text{: x}{}_{22}\text{, ?0.3 cm}{}^{\mathrm{?1}}\text{;}$

$\text{w}{}_2\text{460.2 cm}{}^{\mathrm{?1}}\text{: V}{}_2\text{, 80 cm}{}^{\mathrm{?1}}\text{.}$

     

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.     

Tunable room-temperature cw laser action in Cr3+: GdScAl-garnet

We report, for the first time, cw room temperature laser action of Cr³⁺:Gd₃Sc₂Al₃O₁₂. These crystals show a strong band fluorescence due to the ${}^4\text{T}{}_2\text{→}{}^4\text{A}{}_2$ transition with a lifetime of 150 μs. Laser pumping in the blue and red spectral range yields a minimum threshold of 170 mW and slope efficiencies up to 18.5%. The emission of the free running laser is centered at 784 nm with a FWHW of 5 nm. The extension of the Ga-garnets to Al-garnets as suitable host lattices for Cr³⁺ reveals the variety of garnet-structured crystals having an appropriate ligand field for continuously tunable laser operation.     

Search for 8+ strength in 16O via the 12C(α, α2)12C1(7.66 MeV) reaction

Closely spaced angular distributions have been measured for the ${}^{12}\text{C}\text{(α, α}{}_2\text{)}{}^{12}\text{C}\text{1(7.66}\text{MeV}\text{)}$ reaction between E_α = 17.39 and 20.5 MeV in a search for 8⁺ strength in ¹⁶O. No evidence of 8⁺ strength is found, but evidence is found for a narrow 7^? resonance at 21.52 MeV excitation.     

The Pn values of the 235U(nth, f) produced precursors in the mass chains 90, 91, 93–95, 99, 134 and 137–139

The first results are reported on the P_n values obtained with the recoil focussing parabolatype mass separator for unslowed fission products Lohengrin installed at the Grenoble high flux reactor. The mass chains studied were 90, 91, 93, 94, 95, 99, 134, 137, 138 and 139. Both the neutron and the β activities were measured simultaneously. The technique used to measure the neutron and the β activities and the method of analyzing the experimental data are discussed in detail. The present work led to: (i) three new periods corresponding to the new isotopes of selenium (${}^{91}\text{Se}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 0.27±0.05}\text{sec}$), strontium (⁹⁹Sr, 0.6±0.2 sec) and telurium (¹³⁸Te, 1.3±0.3 sec); (ii) accurate periods of ${}^{99}\text{Y}\text{(T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 1.45±0.22}\text{sec}\text{)}\text{and}{}^{134}\text{Sn}\text{(0.7±0.2}\text{sec}\text{)}$; (iii) four new delayed neutron precursors consisting of ⁹¹Se, ⁹⁴Kr, ⁹⁹Sr and ¹³⁸Te; (iv) six new P_n values corresponding to the precursors ${}^{91}\text{Se}\text{(P}{}_{\mathrm{<mtext>n</mtext>}}\text{= (21±10)\%),}{}^{94}\text{Kr}\text{((5.7±2.2)\%),}{}^{99}\text{Sr}\text{((3.4±2.4)\%),}{}^{99}\text{Y}\text{((1.2±0.8)\%),}{}^{134}\text{Sn}\text{((17±13)\%)}\text{and}{}^{138}\text{Te}\text{((6.3±2.1)\%)}$; (v) a precise P_n value of the precursor ¹³⁷Te ((2.5±0.5)%); (vi) a redetermination of the P_n values of the precursors ^{90, 91}Br, ⁹³Kr, ^{93, 94, 95}Rb and ^{137, 138, 139}I. The results of this work are discussed and compared with the existing data. The low level sensitivity of the present detection system is determined to be $\text{P}{}_{\mathrm{<mtext>n</mtext>}}\text{(m)Y}{}_{\mathrm{q}}\text{(m) ? 0.4 × 10}{}^{\mathrm{?6}}\text{n}\text{/}\text{f}$ (where Y_q(m) is the cumulative yield for the mass m and the ionic charge q).     

Charmed baryon pair production in e+e− annihilation

Cross sections for charmed baryon pair production near threshold in e⁺e^? annihilation are calculated using pole-dominated form factors modified to take intoccount continuum effects. When the C₀⁺$\text{C}$₀^? production cross section is normalized with the help of data for $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→}\text{p}\text{X}$ it is found that the total charmed baryon production cross $\text{(}\text{C}{}_0\text{C}{}_0\text{,}\text{C}{}_1\text{C}{}_1\text{,}\text{C}{}_1\text{C}{}_1{}^1\text{+}\text{C}{}_1{}^1\text{C}{}_1\text{,}\text{C}{}_1{}^1\text{C}{}_1{}^1\text{)}$ reaches a peak value of approximately 2.7 nb at √s = 5 GeV.     

Bound state vibrational spectrum of the 3–9 atom-surface interaction

The potential $\text{V(z) =}\text{C}{}_9\text{z}{}^9\text{?}\text{C}{}_3\text{z}{}^3$ is a reasonable parametrization of the atom-surface interaction. We evaluate the discrete spectrum E_n of bound states for this potential with arbitrary coefficients C₉ and C₃. The resulting form in the WKB approximation is $\text{E}{}_{\mathrm{n}}\text{= ?D [1 ?}\text{(n +}\text{l}\text{2}\text{)}\text{L}\text{]}{}^6$, where L depends on the mass and D is the well depth. We find that the exact solution of the Schrödinger equation can be written in the same form, with n shifted slightly by an amount δ_n, which we calculate. The results are applied to the case of He near a NaF surface, in which the calculated eigenvalue spectrum agrees well with experimental values.