The microwave spectrum of 14NH3 in the v = 000011 state

The frequencies and assignments of 50 lines in the pure inversion spectrum of ¹⁴NH₃ in the 0001¹ vibrational state are reported in the microwave frequency region 18–53 GHz and in selected regions up to 58 GHz.The J = 0 inversion frequency, K-type doubling constant K, l = 2, ?1 and molecular dipole moment in this state are 32 904.7 ± 2.0 MHz, 1.958 ± 0.040 MHz and 1.459 ± 0.002 D, respectively, where model inadequacies are included in the uncertainties of the first two parameters. The dipole moment measurements for this and the ground state are in excellent agreement with Stark laser measurements. An expression containing the effective l-type doubling constant is obtained from the combination of frequencies $\text{[ν(1, 1, 1) ? ν(1, 1, ?1) ? ν(2, 1, 1) + ν(2, 1, ?1)]}\text{8}\text{= 10 361.894 ± 0.004}\text{MHz}$. A preliminary value for the l-type doubling constant is 10 655 ± 20 MHz.     

Theoretical dipole moment function of the X1Σ+ state of HI

Multiconfiguration self-consistent-field calculation has yielded the dipole moment function for the X¹Σ⁺ state of HI, which qualitatively confirms the experimental finding that the dipole derivative at R_e is negative. The calculated dipole moment for the v = 0 vibrational level is 0.665 D for both HI and DI as compared with the experimental values of 0.38 and 0.445 ± 0.02 D, respectively. The calculated potential curve yields values of R_e, D₀, and ΔG_v+1/2, in good agreement with spectroscopic data. A simple valence bond explanation has been provided for the qualitative difference between the dipole moment function of HI and those of the smaller hydrogen halides.     

Intensity of CO2 bands in the 4.8- to 5.3-μm region. The (1110,0310)II-0000 band

Measurements of the line strengths of the (11¹0,03¹0)_II-00⁰0 band of CO₂ (1932.466 cm^?1) have been made with high resolution. They exhibit a strong Coriolis interaction which enhances the P-branch intensity while reducing that of the R branch. The rotationless dipole moment of the transition and the ξ-constant representing this interaction have been determined as: R(0) = (6.57 ± 0.03) × 10^?4D, ξ = ?0.0598 ± 0.0002.     

Spectral intensities in the ν3 bands of 12CH4 and 13CH4

Relative and absolute line intensities for the ν₃ bands of the ¹²C and ¹³C isotopic varieties of methane have been measured using a tunable difference-frequency laser spectrometer. From these data the integrated band strength of ¹³CH₄ is calculated to be 0.983 ± 0.007 that of ¹²CH₄, with the uncertainty representing three standard deviations. The absolute ν₃ bandstrength for ¹²CH₄ is 266.1 ± 3.0 cm^?2 atm ^?1 at 294.7 K where the errors are dominated by the pressure measurement. This band strength corresponds to an effective transition moment 〈μ₃〉 = 0.0534(3)D for ¹²CH₄ from which the ν₄ band dipole moment and the Herman-Wallis F factor can be estimated using a recent force field model for methane.     

Vibrational analysis of the a3Σ+-X1Σ+ and b3Π-X1Σ+ band systems of GeS

Spectra of GeS have been obtained in a chemiluminescent flame produced by the reaction Ge + OCS → GeS + CO. Neither of the known band systems, D¹Π-X¹Σ⁺ and E¹Σ⁺-X¹Σ⁺, was observed, but two new band systems in the regions 350–400 and 420–650 nm were obtained. By comparison with similar systems in isovalent molecules, these were assigned as b³Π₁-X¹Σ⁺ and a³Σ⁺-X¹Σ⁺, respectively. Vibrational assignments were made with the help of the germanium isotope effect and vibrational constants were obtained for the states involved. Approximate Morse potential Franck-Condon factors were computed and were shown to fit the general trend of the intensity distribution for both systems. Addition of active nitrogen to the flame was shown to increase the intensity of the b-X system by an order of magnitude while hardly affecting the a-X system. Constants (in cm^?1) obtained for the two new states are: a³Σ⁺: T_e = 21986.3 ± 2.3, ω_e = 388.9 ± 1.0, ω_ex_e = 1.35 ± 0.11; b³Π₁: T_e = 27192.0 ± 1.8, ω_e = 435.4 ± 1.1, ω_ex_e = 1.68 ± 0.20.     

Spectroscopic analysis of the d1Σ+→a1Σ+ and d1Σ+→b1Π green band systems of XeO

A comprehensive high resolution spectroscopic analysis has been made on the XeO green bands photographed in emission from an RF discharge source. Rotation-vibration constants derived from the analysis of the spectrum of the isotopically enriched species ¹²⁹Xe¹⁶O and ¹²⁹Xe¹⁸O were used to give RKR potential curves for the d¹Σ⁺ and b¹Π states. The bond distances and dissociation energies of the d¹Σ⁺ and b¹Π states were respectively found to be $\text{r}{}_{\mathrm{e}}\text{= 2.852 ± 0.002}\text{A}\text{?}$, D_e = 693 ± 10 cm^?1 and $\text{r}{}_{\mathrm{e}}\text{= 2.548 ± 0.002}\text{A}\text{?}$, D_e = 461 ± 10 cm^?1. For the a¹Σ⁺ state it was not possible to establish a unique vibrational numbering or to construct an RKR potential curve, since observed bands of the d¹Σ⁺→a¹Σ⁺ system involve only high vibrational levels of the a¹Σ⁺ state, which are severely predissociated. The observations are consistent with a fairly deep well, in agreement with the latest ab initio calculations which give a well depth of 0.7 eV.     

Measurement of the magnetic moment of the 7+ isomer in 198Tl

Using the atomic beam magnetic resonance method the hyperfine structure separation of $\text{1.9}\text{h}{}^{\mathrm{198m}}\text{Tl}\text{(I}{}^{\mathrm{\pi }}\text{= 7}{}^{\mathrm{+}}\text{)}$ has been measured in the ${}^2\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ atomic ground state. From the hyperfine structure splitting the nuclear magnetic dipole moment has been deduced. The results are: Δν = 4500 (68) MHz, μ_I = 0.641(10)μ_N. This is an improvement of approximately one order of magnitude compared to a previous measurement. The quoted value of the magnetic dipole moment includes corrections for the hyperfine structure anomaly and for diamagnetic shielding.     

Determination of electric dipole moment for the ν2 vibrational state of 15NH3 by infrared-infrared double resonances

An infrared-infrared double-resonance technique, employing the sidebands produced by electro-optic amplitude modulation of a single-frequency CO₂ laser, is used to observe the second-order Stark effect of the ν₂asR(2, 0) transition of ¹⁵NH₃. The technique enables the Stark shifts in ground and vibrationally excited states to be observed separately and yields the electric dipole moments: μ(v₂ = 1) = 1.253 ± 0.003 D, μ(v = 0) = 1.469 ± 0.004 D. The relative intensity distribution, linewidths, and line shapes of features in the double-resonance Stark spectra are also examined.     

Theoretical calculation of the dipole moment function of the a4Π state of NO

The potential energy curve and theoretical dipole moment function of the a⁴Π state of NO have been determined using full-valence and first-order configuration interaction wavefunctions. Using these two different wavefunctions, the dipole moments of the a⁴Π, v = 3 level have been found equal, respectively, to 0.16 D and 0.30 D, with the polarity N⁺O^?. These values compare well with the value of |0.20 ± 0.04| D determined by Lisy and Klemperer. The first derivative of the dipole moment has also been calculated to be equal to 1.25–1.73 D/bohr.     

Investigation of the 3.46 MeV isomeric level of 38K with the 24Mg(16O,pnγ)38K reaction

The τ_{$\text{1}\text{2}$} = 22 μs isomeric level of ³⁸K at an excitation energy of 3458.0 ± 0.2keVf is strongly populated in the ²⁴Mg(¹⁶O, pnγ)³⁸K reaction. Delayed γ-rays are studied with Ge(Li), Si(Li), and NaI detectors. Accurate excitation energies, branching ratios and lifetimes of levels involved in the decay of the isomeric state are determined. The isomeric level predominantly decays by a dipole transition of 38.03±0.03 keV with a total conversion coefficient of α_T = 0.42 ± 0.15. Mean lives of ³⁸K levels are measured with the recoil-distance method. The results are τ_m = 10.1 ± 0.9 ps, 1.41 ± 0.14 ns and 101 ± 15 ps for the levels at excitation energies of 0.46, 2.65 and 3.42 MeV, respectively. It is suggested that the (1f_{$\text{7}\text{2}$})² structure of a low-lying J^π = 7⁺ state in combination with the selection rules for γ-decay in a self-conjugate nucleus is responsible for the isomerism.     

A new measurement of the Σ+ magnetic moment

A new measurement of the Σ⁺ magnetic moment is reported. The measurement stems from 12 000 events of the reaction K^?p→Σ⁺π^? produced at beam momenta around 460 MeV/c in HYBUC, the hydrogen bubble chamber with an 11.5 T magnetic field. These events represent about 15% of the final statistics. The results from opposite field directions are in close agreement and yield an average value of 2.95 ± 0.31 nuclear magnetons for the total Σ⁺ magnetic moment.     

Electric monopole component in the 2+' → 2+ transition in 192Pt

Angular correlation measurements of K- and L-conversion electrons following the decay ¹⁹²Ir → ¹⁹²Pt have been made using a spectrometer with Ge(Li) and Si (Li) detectors. Absolute and relative internal conversion coefficients of transitions in ¹⁹²Pt were measured, using an ICC and prism β-spectrometers, to ≈ 2 % and values of δ_γ determined from the relative ICC. The experimental values measured in the study, A₂₂(K296γ316) = 0.138 ± 0.010, A₂₂(L296γ316) = 0.125 ± 0.013, α_K(296) = 0.0711 ± 0.0011, K/L_III = 9.65 ± 0.13. With δ_γ = + 5.4 ± 0.2, were employed for determining the E0/E2 amplitude ratios of conversion transitions, q(E0/E2), and the penetration parameter λ of the Ml component for the 2⁺' → 2⁺ (296 keV) transition in ¹⁹²Pt. The angular correlation measurements of L-conversion electrons enabled the elimination of one of two ranges of values of q and λ usually obtained. For the first time in our work, analysis of the e_Lγ angular correlation for the determination of the E0 component in the transition was carried out. As a result, q = +0.04 ± 0.05 with λ = ?4.5 ± 3.5 was obtained for the 296 keV transition. In this case, _ρ(E0) = 0.004 ± 0.005 agrees with _ρ(E0) = +0.006 determined theoretically by Kumar and Baranger for the 2⁺' → 2⁺ transition     

Low-energy transition depopulating the isomeric 8+ level in 208Po

Conversion electron measurements of the low-energy transition depopulating the isomeric 8⁺ level in ²⁰⁸Po yielded E_γ = 4025 ± 20 eV and the conversion intensity ratios N₁/N₂ ? 0.2, N₂/N₃ = 0.75 ± 0.10, N_4.5/N₃ ? 0.2, O/N₃ = 0.35 ± 0.10, P/N₃ ? 0.1 and N₃/M₃ = 0.4 ± 0.2. These ratios are in accord with our calculations for the E2 multipolarity and exclude all other multipolarities with L ≦ 4. The total conversion coefficient was calculated to be 1.31 × 10⁷.     

Radiative lifetime of NaH A1Σ+ in a high frequency discharge

The radiative lifetimes of NaH, A¹Σ⁺, excited states have been measured by pulsed dye laser excitation. The hydride is obtained by h.f. discharge in hydrogen and metal vapor, at a total pressure less than 10^?1 Torr. The measured lifetimes are: (24.0 ± 3.0) ns for v′ = 3, J′ = 8; (28.3 ± 3.0) ns for v′ = 4, J′ = 11; (27.1 ± 3.0) ns for v′ = 5, J′ = 16.     

Theoretical integrated intensities for the 2ν2 and 2ν2-ν2 bands of HCN and DCN

Dipole moment functions, both perpendicular and parallel to the molecular axis, are calculated from the SCF and MRD-CI results of a previous study for the normal ν₂ bending vibrations of HCN and DCN. Vibrationally averaged dipole moments and the infrared transition matrix elements are then obtained from the dipole moment functions and vibrational wave functions. MRD-CI results, with known experimental values in parentheses, for HCN are 〈0|μ|0〉 = ?2.954(?2.985) D, 〈1|μ|1〉 = ?2.915(±2.942) D, 〈0|μ|1〉 = 0.148(0.147) D, 〈0|μ|2〉 = ?0.027 D, 〈1|μ|2〉 = 0.210 D. Calculated absolute intensities at 1 atm and 0°C for the (02⁰0) ← (000), (02⁰0) ← (010), and (02²0) ← (010) bands of HCN are 25 (40 ± 10 as estimated from spectra), 8.5, and 17.0 atm^?1 cm^?2, respectively. Results for DCN are also reported.     

Elastic electron scattering from the magnetization distribution of 27Al

Cross sections have been measured for the scattering of electrons through 180° from Mg, Al and Si targets in the energy range 35 to 95 MeV. Scattering from the magnetization distribution of ²⁷Al is observed as the difference of the scattering from ²⁷Al and from the neighbouring doubly even nuclei Mg and Si. Corrections have been applied for differences in instrumental effects and in rms charge radii. Theoretical magnetic cross sections have been computed with a single-particle wave function and with a shell-model wave function involving configuration mixing. If the distorted-wave Born approximation is used, good agreement with experiment is obtained. In both cases the best fit to the data yields a value of the oscillator range parameter b = 1.71 ± 0.06 fm. Using the q-dependence of the single-particle model a value $\text{Ω = 18.7 ± 3.5 μ}{}_{\mathrm{<mtext>N</mtext>}}\text{·}\text{fm}{}^2$ for the magnetic octupole moment of ²⁷Al is found. The present low-energy (E < 100 MeV) data are in good agreement with the results obtained from the scattering of high-energy (E = 500 MeV) electrons from ²⁷Al through “normal” angles.     

Diode laser measurements of intensities,N2-broadening,and self-broadening coefficients of lines of the ν2 band of 14N16O2

A diode laser spectrometer (resolution 0.0013 cm^?1) was used to record, in the 12-μm region, high-quality spectra of the ν₂ band of NO₂. Using these spectra, it was possible to obtain the N₂-broadening coefficients and an average self-broadening coefficient from measurements made for seven lines of this band. In addition, 30 single spin-component line intensities were measured. From them, through a least-squares fit, the purely vibrational transition moment of the ν₂ band, as well as two correcting rotational terms involved in the expansion of the transition moment operator, were obtained. These results led to the determination of the dipole moment derivative $\text{?μ}{}_{\mathrm{x}}\text{?q}{}_2\text{= ?0.0604}{}_1\text{± 0.0037}\text{D}$. It was also demonstrated that there is good consistency between the correcting terms deduced from the observed intensities and their theoretical estimates. Finally, a complete spectrum of the ν₂ band of NO₂ was computed, providing a total band intensity S_v(ν₂) = 0.542 × 10^?18cm^?1/molecule cm^?2 at 296 K.     

The g-factor of the 6+ state in 50Ti

The rotation of the angular distribution pattern of the 524 keV γ-radiation from the 6⁺, 3200 keV state in ⁵⁰Ti was measured in an external magnetic field using the ⁴⁸Ca(α, 2n) reaction. The IPAD method was applied. From the experimental precession angle, the value of the g-factor, g = 1.57 ± 0.17, has been derived.     

Measurement of the φ→π+π− branching ratio

The branching ratio of the φ→π⁺π^? decay mode B_{φππ = (1.9?0.8^+1.0) × 10^?4} was measured by the interference in the reaction e⁺e^? → π⁺π^?. The interference phase ψ = ?42° ± 13°. The value of χ² for B_φππ = 0 is 17.8 units larger than that for the optimal B_φππ, e.g.B_φππ = 0 lies outside of the four standard deviation confidence interval.     

Measurement of the parity non-conservation in nuclear forces in 75As, 171Tm,and 175Lu and of the polarized bremsstrahlung from 51Cr, 170Tm, 177Lu,and 198Au

The circular polarization P of γ-rays from unpolarized sources of ⁷⁵Se, ¹⁷¹Er, and ¹⁷⁵Yb of strengths ? 500 Ci has been measured with a Compton polarimeter of the radial transmission type. Eight NaI crystals and a four-fold current integration system were used to simultaneously record the data in four independent channels. The results are: P = ?(1.8 ± 6.0) × 10^?5 for the 401 keV transition in ⁷⁵As (the experimental error is ± 1.5 × 10^?5, the remaining part is due to the uncertainty in the decay scheme of ⁷⁵Se), P = (0.8 ± 1.5) × 10^?4 for the 296 keV and 308 keV transition in ¹⁷¹Tm, and P = (5.7 ± 0.8) × 10^?5 for the 396 keV transition in ¹⁷⁵Lu. The last value confirms the parity non-conservation in nuclear forces. The polarimeter was calibrated with bremsstrahlung from ¹⁷⁰Tm. The correction for polarized bremsstrahlung was given special attention. Correction factors are derived for ⁵¹Cr, ¹⁷⁷Lu, and ¹⁹⁸Au from a comparison of the measured and calculated bremsstrahlung yields.