Search for a narrow resonance in 6Be with the 4He(3He,n) reaction

The ⁴He(³He, n)⁶Be reaction has been investigated at 36.20 MeV bombarding energy in search for a narrow resonance near the ³He-³He threshold which has been proposed as a possible explanation for the missing solar neutrinos in Davis' experiment. Neutrons have been detected at θ_b = 0° with an effective resolution < 25 keV in the c.m. system, in coincidence with protons emitted at θ_p = 50°. No indication for the existence of such a resonance has been found and an upper limit (dσ/dω)_res ≦ 7.5 μb/sr has been established.     

Low-energy behavior of the 3He(α, γ)7Be cross section

Cross sections for the ³He(α, γ)⁷Be reaction have been measured at several energies from E_c.m. = 165 to 1169 keV by counting prompt γ-rays from a windowless, differentially pumped, recirculating, ³He gas target. The cross-section factor S₃₄(E_c.m.) and branching ratio γ₁/γ₀ were determined at each energy. Cross sections were also measured at E_c.m. = 947 and 1255 keV by counting the γ-rays from the ⁷Be produced in a ³He gas cell with a Ni entrance foil. Combining the results of these two independent experiments yields a zero-energy intercept for the cross-section factor of S₃₄(0) = 0.53 ± 0.03 keV · b. The relationship between these measurements and several theoretical calculations, and the import of the extrapolated cross section for the solar-neutrino problem are discussed.     

Initial-state distortion and final-state interactions in the 2H(3He, 3He p)n and 2H(3He, 3H p)p reactions

The predictions of two fully antisymmetrized reaction theories (DWBA and PWBA-FSI) are compared with absolute coincidence cross sections for the ²H(³He, ³He p)n and ²H(³He, ³H p)p reactions exhibiting final-state interactions (FSI) and quasi-elastic scattering (QES) both with and without charge exchange. The DWBA theory takes into account both the initial ³He-d and the final N-N interactions, while the PWBA-FSI theory includes only the latter. New QES data at E_He = 35.9 MeV, as well as previously reported 26.8 and 35.9 MeV data, are fitted. The DWBA theory gives good fits, both in shape and magnitude, to spectra showing N-N final-state interactions but gives somewhat poorer fits to QES spectra whose predicted magnitudes are two to ten times too large. The PWBA-FSI theory always predicts cross sections that are too large; however the predicted shapes are about as good as those from the DWBA. The initial-state interaction is shown to affect both the width and position of QES peaks from these reactions.     

The vibrational transition moment for the ν2 bands of 14ND3 and 15ND3

Intensities were measured at high pressure (200 Torr) for blended K-multiplets in the P and R branches of the s0 → aν₂ and a0 → sν₂ bands of ¹⁴ND₃. Intensities of 55 individual lines at 10 Torr of ¹⁵ND₃ were also measured by deconvolution of the true line shape from the observed vibration-rotation spectrum and the instrumental line shape. From these results we estimate a transition moment of 0.179 ± 0.010 D for both ¹⁴ND₃ and ¹⁵ND₃. These lead to a derivative of the dipole moment, $\text{|}\text{?μ}\text{?Q}{}_2\text{| = 93}\text{cm}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{sec}{}^{\mathrm{?1}}$.     

Intensities of the v1-bands of 12CH335Cl and 12CH337Cl near 3 μm

Strengths of individual lines in the v₁ fundamental of methyl chloride have been measured at low pressure and at 296.35 K using a Fourier transform interferometer. The band strengths S_v⁰ obtained by fitting these measurements are 85.8±1.0 and 86.6±1.0 cm^-2 atm^-1 for ¹²CH₃³⁵Cl and ¹²CH₃³⁷Cl, respectively. The Q₃-branch appears to be useful for atmospheric detection of methyl chloride.     

The 51V(p,n)51Cr reaction at Ep = 160 MeV

The ⁵¹V(p, n)⁵¹Cr reaction has been studied at E_p = 160 MeV using the Indiana University beam-swinger facility. Data have been obtained at several angles up to θ_L = 20°. The 0° spectrum is used to obtain a ΔL = 0 response function from which Gamow-Teller strength is derived. A shell-model calculation of the GT strength distribution is presented and compared with the experimental results. The M1 strength is also calculated and compared with available results from (e, e') and (p, p') experiments. A comparison is made with other N = 28 nuclei. Effects of a truncated shell-model space are presented.     

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.     

Reactions of 40Ar with 159Tb, 142Nd and 144Sm; New α-activities from 189Bi, 173Pt and 177Au

Reactions of ⁴⁰Ar ions with targets of ¹⁵⁹Tb, ¹⁴²Nd, and ¹⁴⁴Sm have been studied at energies below 300 MeV with a helium gas-jet system. Excitation functions for (Ar, xn) reactions, where x = 5–10, were obtained for the radioactive products that decay by α-emission. Based on the characteristics of these excitation functions and on the systematics of α-decay, evidence is presented for the existence of the nuclides ¹⁸⁹Bi with α-particle energy E_α = 6.67±0.01 MeV and half-life < 1.5 sec, and ¹⁷³Pt with E_α = 6.19±0.01 MeV; and for the emission from ¹⁷⁷Au of an α-particle with E_α = 6.15±0.01 MeV.     

Effects of exchange and final-state interactions in the reactions 2H(3He, 3H p)p and 2H(3He, 3He p)n

Absolute coincidence cross sections for the ²H(³He, ³He p)n and ²H(³He,³H p)p reactions were measured at E_He = 35.9 MeV. Spectra dominated by the nucleon-nucleon final-state interaction (FSI) are fitted by a fully antisymmetrized PWBA theory which includes the effects of FSI in all its matrix elements. Previously reported 26.8 MeV data showing both FSI and quasi-elastic scattering (both with and without charge exchange) are also fitted by the theory, which qualitatively describes the shapes of all these spectra and the ratios of the cross sections for the various processes. Predictions of Watson-Migdal theory are fitted to the FSI spectra and differences between the two theories are analyzed.     

Band analysis of the Swan system (d3Πg-a3Πu) of 13C2 and 12C13C molecules

The emission spectrum of the d³Π_g-a³Π_u system (Swan bands) due to ¹³C₂ and ¹²C¹³C molecules has been obtained in a low pressure hollow cathode discharge through a mixture of argon and benzene containing enriched ¹³C (90%). The spectrum was photographed on a 3.4-m Ebert spectrograph (reciprocal dispersion 0.54 Å mm^?1 in the first order). Isotope effect measurements have been carried out to determine the shift between isotopic bands and those emitted by ordinary molecules. The rotational analysis of six ¹³C₂ bands and three bands of ¹²C¹³C has been performed and molecular constants were derived.     

Diffusion of 55Fe in Fe2O3 single crystals

The diffusion of ⁵⁵Fe has been measured parallel to the c axis of Fe₂O₃ single crystals at temperatures in the range 708–1303°C and at an oxygen activity of unity. The tracer penetration profiles were determined using sectioning techniques. For temperatures above 900°C the tracer diffusion coefficient is given byD¹(Fe) = 1.6 × 10⁹ exp[?6.0 (eV)/kT] cm² s^?1 and below 900°C by 2.8 × 10^?9 exp[?1.8 (eV)kT]. The high-temperature behaviour is probably characteristic of pure Fe₂O₃, whereas diffusion at lower temperatures may be influenced by impurities. The most likely defects responsible for diffusion of Fe are iron interstitials and, for oxygen, oxygen vacancies, and the observed activation energies are discussed in terms of the properties of these defects. The diffusion data and defect models have been used to predict the rate of growth of Fe₂O₃ and indicate that outward Fe diffusion is the dominant transport process. Previously published data for Fe₂O₃ growth in a variety of experimental situations have been corrected to a single rate constant using a model for multilayer growth. The corrected data are all in good agreement but are approximately two orders of magnitude greater than predicted from diffusion data, which suggests that grain boundary diffusion controls the growth of Fe₂O₃ in practice.     

The 12C(9Be,n)20Ne reaction

A study of the ¹²C(⁹Be, n)²⁰Ne reaction has been carried out at bombarding energies of 16 and 24 MeV. The spectra at both incident energies are dominated by a consistent set of levels between an excitation energy of 7.3 ± 0.4 and 15.7 ± 0.3 MeV. The rotational band based on the K^π = 0₃⁺ state appears to be strongly populated. Based on this selectivity, additional evidence is provided in favor of identification of the 8⁺ state at 15.9 MeV with this 0₃⁺ band. Angular distributions measured at the higher bombarding energy are compared with statistical compound-nuclear calculations. It appears that a non-statistical mechanism is responsible for the reaction's selective population of states with 8p-4h configuration. Such a mechanism, involving the preferential breakup of the ⁹Be into ⁸Be plus a neutron, is discussed.     

The elastic scattering of 3He on 4He at medium energies

The differential cross section of the elastic scattering ³He(⁴He, ⁴He)³He has been measured at center of mass energies E_c.m. between 28 and 44 MeV and in the c.m. angular range of 20° to 160°. The ³He polarization P at E_c.m. = 42 MeV and θ_c.m. = 132° was determined in a double scattering experiment. The analysis of the cross section data with the optical and the cluster model has been described previously. The phase shifts obtained in the cluster model calculations were used as starting values in a phase shift analysis. The resulting final real phase shifts and elasticity parameters give good fits to the cross section data. At 44 MeV the elasticity parameters show a pronounced odd-even dependence on angular momentum which had been found already in the case of the real phase shifts. The result of the polarization experiment |P| < 0.22 is consistent with cluster model predictions.     

Identification and intensities of the “forbidden” 3ν23 band of 12C16O2

Lines of the 3ν₂³ “forbidden” band of ¹²C¹⁶O₂ have been identified in the 2000-cm^?1 region of a long-path, 0.01-cm^?1 resolution laboratory absorption spectrum. This band has detectable intensity due to Δl = 2 Fermi interactions between the upper level and the nearby ν₁ + ν₂ and 3ν₂¹ levels. Intensities of 18 lines of this band have been measured using a nonlinear least-squares spectral fitting technique. The intensities are enhanced at high J and an expression for the intensity distribution as derived by Toth [Appl. Opt.23, 1825–1834 (1984)] is used for the analysis. In terms of the total sample pressure, the vibrational band intensity is 0.194 ± 0.008 × 10^?30 cm^?1/molecule-cm^?2 at 296 K. The coefficient in the F factor is analogous to the Coriolis coefficient ξ and has been determined to be ?0.0413 ± 0.0015. As expected by theory, its value is very close to that of ξ for the related ν₁ + ν₂ band.     

A study of the 2H(d,p)3H AND 2H(d,n)3He reactions and the excited state of 4He at 23.9 MeV

The relative differential cross sections have been measured for the ²H(d, p)³H and the ²H(d, n)³He reactions from 300 keV to 700 keV in 50 keV steps. Angular distributions of all charged particles from the reactions were taken from 20° to 160° in the laboratory system. Energy-dependent asymmetry coefficients from the expansion of the centre-of-mass angular distributions in terms of even powers of cos θ were obtained as were the branching ratios between the two reaction modes. The different energy dependences of the moments of the two cross sections were used to test the need for the existence of a recently reported T = 0 state in ⁴He.     

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.     

The torsion-rotation microwave spectrum of 12CH318OH and the structure of methanol

The microwave and millimeter wave spectrum of ¹²CH₃¹⁸OH has been observed in the frequency region 7.9–200 GHz. Both a- and b-type transitions have been assigned and measured. This spectrum was analyzed using the method of Lees and Baker, and rotational constants, torsional constants, centrifugal distortion constants, the barrier to internal rotation and moments of inertia have been evaluated. The barrier has been found to be 374.91 ± 0.18 cm^?1, in good agreement with that of ¹²CH₃¹⁶OH. The moments of inertia were combined with those of other isotopic species to give a full substitution structure. To assist searches for this molecule in interstellar space a table of predicted frequencies of astrophysically interesting transitions is presented.     

Doubly radiative neutron capture by 2H, 3He, 16O and 208Pb

Cross-sections for doubly radiative thermal neutron capture on ²H, ³He, ¹⁶O and²⁰⁸Pb are calculated to be 21, 1200, 41 and 50 nb, corresponding to branching ratios of σ(n, γγ)/σ(n, γ) = 4.0 × 10^?5, ～ × 10^?2, 2.2 × 10^?4 and 1.0 × 10^?4, respectively.     

59Co nuclear magnetic resonance in antiferromagnetic CsCoCl3

The ⁵⁹Co NMR in a CsCoCl₃ single crystal has been observed by the spin echo method at 4.2 K. The obtained spectrum is composed of seven distinct lines split by the nuclear-quadrupole interaction. The frequency of the central (± $\text{1}\text{2}$ ? ± $\text{1}\text{2}$) transition 502.08±0.05 MHz corresponds to the hyperfine field of 499.38 ± 0.05 kOe, which agrees well with the calculated value. Due to the interaction of the nucleus with the electronic moment induced by the external field, a shift as large as 18% was observed for the nuclear g-factor.     

Simultaneous analysis of the microwave and infrared spectra of 14ND3 and 15ND3 for the ν2 excited state

The data on the inversion spectrum in the ν₂ state of ¹⁴ND₃ [F. Scappini, A. Guarnieri, and G. DiLonardo, J. Mol. Spectrosc.95, 20–29 (1982)] have been extended by measuring frequencies of 25 new transitions. A simultaneous least-squares analysis of these data with the ground state microwave transition frequencies and the diode laser measurements of the ν₂ band has been carried out. Improved sets of molecular parameters have been obtained for ¹⁴ND₃ and ¹⁵ND₃, including the ground and ν₂ state inversion splittings, ν₂ band origins, rotational and centrifugal distortion constants, and the parameters of the Δk = ±3n vibrational-rotational interactions.