A spectroscopic study of 18F: (I). The 17O(p,p)17O and 17O(p, α0)14N reactions

The ¹⁷O(p, p)¹⁷O and ¹⁷O(p, α₀)¹⁴N reactions have been studied in the energy range E_p = 0.5–1.33 MeV. Excitation functions for elastic scattering measured at several angles give l_p values for six resonances and J^π; T values of 3⁺; 1 and 2⁺; 1 for the states at 6.16 and 6.28 MeV, respectively. From both reactions, J^π limitations were found for six resonant levels. The ¹⁷O(p, α₀)¹⁴N reaction also yields information on T-assignments and level formation parameters. Experimental results are discussed in terms of shell-model configurations.     

Etude de 17N par la reaction 18O(t, αγ)17N

The first six excited states of ¹⁷N have been studied by using the ¹⁸Ot, αγ)¹⁷N reaction at a bombarding energy of E_t = 3.5 MeV. Alpha-gamma angular correlation measurements (method II) were used to determine spins, mixing ratios and branching ratios. The 1.37, 1.85, 1.91, 2.53, 3.13 and 3.20 MeV levels have been assigned the spins $\text{3}\text{2}$, $\text{1}\text{2}$, $\text{5}\text{2}$^?, $\text{5}\text{2}$⁺, $\text{7}\text{2}$ and $\text{3}\text{2}$ respectively. Excitation energies are also given. Most of the results are in good agreement with previous data or suggested values. Mixing ratios have been obtained for the first time. The level scheme of ¹⁷N is compared with some $\text{T =}\text{3}\text{2}$ analogue states in ¹⁷O and ¹⁷F and with results of recent shell-model calculations.     

The decay of the18O giant dipole resonance to excited residual nuclear states

The decay of the¹⁸O GDR to excited residual nuclear states has been examined by measuring spectra of prompt deexcitationγ-rays. The target was irradiated by bremsstrahlung with endpoint energies of 23.5 and 28 MeV. “Bremsstrahlung-weighted” integrated cross sections are given for the population of the residual nuclear states in¹⁷O,¹⁷N,¹⁶O and¹⁴C. Proton decay to excited states in¹⁷N is remarkably weak. It seems that 1p _3/2 excitations play only a minor role in the¹⁸O GDR.     

The 17O(p, α)14N reaction: Physics and astrophysics

The nucleus ¹⁸F has been studied using the ¹⁷O(p,α)¹⁴N reaction over the energy range E_p = 400 to 1400 keV with thin Ti¹⁷O₂ targets. New resonances at E_p = 525, 688, 1015, 1276 and 1338 keV have been discovered. The strengths for all resonances in this energy range have been measured and the entire cross section in this region has been fitted using the R-matrix formalism of Lane and Thomas. Some discussion is presented concerning the values of the boundary condition parameters used in the R-matrix fit and two sets of results are presented corresponding to two different treatments of the boundary conditions.The ¹⁷O(p, α)¹⁴N cross section has been extrapolated to astrophysical energies using an R-matrix calculation incorporating the partial widths obtained from the data from E_p = 400 to 1400 keV. These results are compared with previous ¹⁷O(p, α)¹⁴N calculations and the ¹⁷O(p, γ)¹⁸F direct capture calculation of Rolfs and Rodney.     

Investigation of states in17F by the15N(3He,n)17F reaction

The absolute differential cross sections for several levels in the¹⁵N(³He,n)¹⁷F reaction were measured at laboratory scattering angles from 0 to 140 degrees using neutron time-of-flight techniques. Angular distributions were obtained at effective helion bombarding energies of 3.8 and 4.8 MeV. A new state was identified at 5.18 ±0.02 MeV excitation energy which is probably the analogue of the 5.217 MeV state in¹⁷O. Spectroscopic factors were obtained for the low-lying states using distorted wave method calculations.     

Reaction cross sections in Si of light proton-halo candidates 12N and 17Ne

Total reaction cross sections, σ_R, on Si were measured near 40 A MeV for the proton-halo candidate ¹²N and the two-proton-halo candidate ¹⁷Ne, and were compared with σ_R for other light proton-rich nuclei. The A-dependence shows enhanced σ_R's for ¹²N and ¹⁷Ne, relative to their neighbors, but the effect is smaller than for ⁸B which has been argued to have a proton halo. In general, nuclei with loosely bound last protons (S_p ⩽ 1.5 MeV) have significantly larger σ_R's than their neighbors. Cross sections for charge-removal from ¹²N and ¹⁷Ne also were obtained.     

Nuclear magnetic resonance of intermetallic compounds Gd2Ni17−xAlx

²⁷Al Knight shifts vs temperature and magnetic susceptibility for the intermetallic compounds Gd₂Ni_17?xAl_x (x = 17; 16.2; 16; 15) are presented. The results are discussed in terms of the uniform polarization model fo the conduction electrons by the 4f and 3d spins localized on the Gd and Ni ions. The phenomenological exchange constants J_sf and J_sd range between ?1.80×10^?3 and 1.19×10^?3 eV and ?0.63×10^?3 and ?0.52×10^?3 eV, respectively.     

Search for resonances in 12C(9Be, α)17O

Excitation functions at 7° (lab) have been measured from E_c.m. = 5.1 to 11.4 MeV in approximately 114 keV steps for 15 groups of final states in ¹⁷O populated by the ¹²C(⁹Be, α) reaction. Statistical tests have been used to locate possible non-statistical structure in the excitation functions. Possible anomalies were found near E_c.m. = 6.3, 7.5, 8.9 and 9.7 MeV. Angular distributions were measured at E_c.m. = 9.20, 9.71 and 10.23 MeV for the three lowest excited states in ¹⁷O. The data have been compared with Hauser-Feshbach calculations in addition to the following reaction mechanisms: compound plus a single resonance, compound plus interfering resonances and compound plus direct reactions.     

Nitrogen 1s electron binding energy assignment in carbon nitride thin films with different structures

Carbon nitride thin films deposited by dc unbalanced magnetron sputtering have been analyzed by high-resolution X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The XPS data show that N 1s binding states depend on substrate temperature (T_s). By comparison with the Raman spectra, N 1s binding states are assigned in which nitrogen atoms are mainly bound to sp² and sp³ carbon atoms at T_s = 100°C, whereas at T_s = 500°C nitrogen atoms are mainly bonded to sp², sp³ and sp¹ carbon atoms.     

The Jπ = 3− doublet at Ex = 6241 keV in 18F: Isospin mixing

The resonance previously observed at E_x = 6241 keV in the reactions ¹⁷O(p, γ)¹⁸F and ¹⁴N(α, γ)¹⁸F has been found to be a closely separated doublet (ΔE_x = 2.09±0.04 keV). Resonance strengths in ¹⁷O(p, γ)¹⁸F, ¹⁷O(p, α)¹⁴N and ¹⁴N(α, γ)¹⁸ have been measured and partial widths for the resonance states have been obtained. The doublet was further investigated by means of the ⁴He(¹⁴N, α)¹⁴N reaction using the differentially pumped gas target at CRNL. Analysis of these data using R-matrix theory yielded J^π = 3^? for both states and more precise values of the α-particle widths (Γ_α(lower) = 133 ±4 eV; Γ_α(upper) = 137 ±4 eV). The reduced α-particle widths and the E1 and M1 transition strengths indicate that the doublet arises from the nearly complete mixing of T = 0 and T = 1 eigenstates which in the absence of an isospin breaking interaction would have been separated by less than 40 eV. The α-particle scattering experiments included the J^π = 1⁺ resonance at E_x = 6257 keV and yielded the new values of Γ_α = 580±12 eV and Γ_p = 25⁺³⁵_?25 eV.     

Effects of annealing ambience on ZnO:N films grown by MOCVD and the p-type doping mechanism of ZnO:N films investigated by XANES

ZnO:N thin films were deposited on sapphire substrate by metal organic chemical vapor deposition with NH₃ as N-doping sources. The reproducible p-type ZnO:N film with hole concentration of ∼10¹⁷ cm⁻³ was successfully achieved by subsequent in situ thermal annealing in N₂O plasma protective ambient, while only weak p-type ZnO:N film with remarkably lower hole concentration of ∼10¹⁵ cm⁻³ was obtained by annealing in O₂ ambient. To understand the mechanism of the p-type doping behavior of ZnO:N film, X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption near-edge spectroscopy (XANES) measurements have been applied to investigate the local electronic structure and chemical states of nitrogen atoms in ZnO:N films.     

Centrifugal distortion analysis of pure rotational spectra of H216O,H217O,and H218O

Centrifugal distortion analyses based entirely on high-quality infrared data are carried out for the ground vibrational states of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O. As a result of the analyses, the values of 27 rotation and distortion constants for each species are determined. By using these constants it was possible to improve considerably the accuracy of the literature values for rotational energy levels at high J_τ, especially for H₂¹⁷O and H₂¹⁸O. The experimental values for the energy levels are deduced from the observed rotational transitions constituting the fitted data.     

The interacting states (020), (100), and (001) of H217O and H218O

A fit of about 350 rotational levels of the (020), (100), and (001) vibrational states has been performed for H₂¹⁷O as well as for H₂¹⁸O leading to the determination of 51 rotational and coupling constants for each isotopic species. The Fermi-type interaction and the two Coriolis-type interactions have been taken into account by appropriate rotation-vibration operators and the v-diagonal part of the Hamiltonian is, for each vibrational state, a Watson-type Hamiltonian. The results are very satisfactory since 87% of the experimental levels are reproduced within 15 × 10^?3 cm^?1.     

Spectroscopy of intermediate 16F states with the reaction 14N(3He,np)15O

Excited states of ¹⁶F have been investigated with the reaction ¹⁴N(³He, np)¹⁵O at E = 10.5 and 12 MeV in kinematically complete experiments. Proton groups corresponding to the decays of intermediate ¹⁶F states were observed at various angles with counter telescopes in time coincidence with the associated neutrons detected at θ_n^lab = 0° with a time-of-flight spectrometer. Excitation energies and decay widths Γ_p0 of these states have been extracted from the proton spectra. Lower limits for the orbital angular momentum in the decay channel and for the spin of the states have been deduced from the obtained angular correlations. By comparison with the reaction ¹⁴N(³He, pp)¹⁵N measured at E = 13 MeV, pairs of $\text{T = 1}{}^{16}\text{F}$ parent/¹⁶O analog states have been identified. J^π assignments and shell-model configurations are discussed on the basis of the selectivity of the reactions measured.     

Parity violation in the 17/2− isomer of93Tc

The parity-violating mixing of the 17/2^? and 17/2⁺ levels in⁹³Tc nuclei, polarized by the tilted multifoil interaction, was measured by the observation of the forwardbackwardγ-ray asymmetry. The asymmetry was determined to beA _γ=1.18(48)×10^?3. The nuclear polarization was determined in a measurement of the quadrupole interaction in a⁹²Mo isomer and the parity violation matrix element 〈H _PV〉 is found to be ¦〈H _PV〉¦ =0.8(4) meV.     

Nuclear structure of 18F: (IV). Negative-parity states

Studies via the ¹⁶O(³He, pγ)¹⁸F, ¹⁴N(α,γ)¹⁸F and ¹⁷O(p, γ)¹⁸F reactions have resulted in new J^π assignments for 11 states or negative parity: E_x(keV) (J^π) = 3791(3^?), 4226(2^(?)), 4398(4^?), 4860(1^(?)), 5502(3^(?)), 5785(2^?), 6097(4^?), 6108(1^(?), 2^(?), 3^(?)), 6241(3^?, T = 1), 6643(2^?, T = 1) and 6878(3^(t-), 4^?). The 6241 keV state is probably isospin mixed. New information for 5 states of positive parity has also been obtained: E_x(keV) (J^π) = 3838(2⁺), 4115(3⁺), 4652(4⁺, T = 1), 4753((0⁺), T = 1) and 4964(2⁺, T = 1). Mean lives, branching and mixing ratios are reported for all states. The results for the negative-parity states are discussed in the framework of the various models available. The states at E_x = 1080(0^?), 2100(2^?) and 4398(4^?) keV are interpreted as the first three members of a K^π = 0^? rotational band.     

Rotational analysis ofA 1Π-X 1Σ+ bands of As14N and As15N: perturbation studies in theA 1Π state

The ultraviolet bands ofA ¹Π-X ¹Σ⁺ system of As¹⁴N and its isotopic species As¹⁵N were excited in a quartz tube containing specpure nitrogen and traces of AsCl₃ vapour, using a microwave discharge (2450 MHz). Bands of As¹⁵N were obtained using¹⁵N₂ enriched to 95.5%. Rotational structure of several bands of As¹⁴N and As¹⁵N photographed under high dispersion (0.14 Å/mm) was reanalysed. Detailed studies of the observed perturbations in the levels ofν′ = 0 to 4 led to the identification of two³Σ^? and aC ¹Σ^? states. Molecular parametersT _e, ω_e, ω_ex_e, B_eandα _ewere determined for all the electronic states studied. Vibrational assignments of the perturbing levels were made using the isotope shift studies.     

High-Temperature Infrared Emission Spectra of DCN and DCN

The infrared spectra of two isotopomers of deuterium cyanide, D¹²C¹⁴N and D¹³C¹⁴N, were measured in emission at temperatures of 1370 K and 1520 K, respectively, in the range from 450 to 850 cm⁻¹ and, for D¹²C¹⁴N, also from 1800 to 2800 cm⁻¹. Assignments were made for rovibrational transitions to high bending states, v₂=9 for D¹³C¹⁴N and v₂=11 for D¹²C¹⁴N. To aid and verify the assignments, bands of the lower bending states, up to v₂=3, were also measured in absorption at room temperature. A global fit was made of all measurements available to us for each isotopomer. In addition to giving the rovibrational constants for each state measured, the power series expansion constants are also given and compared with those of the other deuterium cyanide isotopomers. The D¹²C¹⁴N laser transitions are verified as arising from the consequences of the Coriolis interaction between the J=21 levels of the 02⁰2 and 09^1e0 states.     

Optical spectra of (CdF2)0.9(InF3)0.1 semiconductor solid solutions

The differences in the optical spectra of CdF₂:In semiconductors with bistable DX centers (concentrated (CdF₂)_0.9(InF₃)_0.1 solid solutions) and “standard” samples with a lower impurity concentration used to record holograms are discussed. In contrast to the standard samples, in which complete decay of two-electron DX states and transfer of electrons to shallow donor levels may occur at low temperatures, long-term irradiation of a (CdF₂)_0.9(InF₃)_0.1 solid solution by UV or visible light leads to decay of no more than 20% deep centers. The experimental data and estimates of the statistical distribution of electrons over energy levels in this crystal give the total electron concentration, neutral donor concentration, and concentration of deep two-electron centers to be ～5 × 10¹⁸ cm^?3, ～9 × 10¹⁷ cm^?3, and more than 1 × 10²⁰ cm^?3, respectively. These estimates show that the majority of impurity ions are located in clusters and can form only deep two-electron states in CdF₂ crystals with a high indium content. In this case, In³⁺ ions in a limited concentration (In³⁺ (～9 × 10¹⁷ cm^?3) are statistically distributed in the “unperturbed” CdF₂ lattice and, as in low-concentrated samples, form DX centers, which possess both shallow hydrogen-like and deep two-electron states.