NMR observation of the spin structure and field induced spin reorientation in YFeO3

For the first time the ⁵⁷Fe NMR spectrum of the nuclei in the domains of a YFeO₃ single crystal has been observed. The splitting of the lines by an external magnetic field allows a very exact determination of the spin orientation of the four Fe sublattices. The ferro- and antiferromagnetic canting angles in zero field are φ = 12.3 mrad and ψ = 14.0 mrad, respectively. The field-induced spin reorientation can be described using the model of antisymmetric exchange interaction including second- and fourth-order anisotropy constants.     

Shell model isomers near Z = 64, N = 82: g-factors of Yrast states in 146Gd and 147Gd

Nuclear g-factors have been measured for the 7^? isomer in ¹⁴⁶Gd and for the $\text{27}\text{2}{}^{\mathrm{?}}$ isometer in ¹⁴⁷Gd. For ¹⁴⁷Gd the results is consistent with the expectation for a pure shell model configuration.     

Quadrupole coupling in EuO due to lattice imperfections

From ¹⁵³Eu nuclear spin-spin relaxation measurements it is concluded that quadrupole effects observed in ferromagnetic EuO are due to lattice imperfections.     

Determination of chlorophyll in plant samples by liquid chromatography using zinc-phthalocyanine as an internal standard

Chlorophyll analysis at high precision and accuracy is limited by the lack of suitable, commercially available internal standards for HPLC analysis. Here, the commercially available dye zinc-phthalocyanine is presented as a new internal standard to quantify chlorophylls in vegetable foods and to detect chlorophyll degradation products. The technique was applied to chlorophyll analysis of a selection of vegetable foods. Pigments were extracted with N,N-dimethylformamide from the vegetables and purified by solid phase extraction. Chlorophyll a, a', b, b', corresponding pheophytins, and zinc-phthalocyanine were separated by HPLC using a C18 reverse-phase column and fluorescence detection.     

Acoustic and perceptual similarity of North German and American English vowels

Current theories of cross-language speech perception claim that patterns of perceptual assimilation of non-native segments to native categories predict relative difficulties in learning to perceive (and produce) non-native phones. Cross-language spectral similarity of North German (NG) and American English (AE) vowels produced in isolated hVC(a) (di)syllables (study 1) and in hVC syllables embedded in a short sentence (study 2) was determined by discriminant analyses, to examine the extent to which acoustic similarity was predictive of perceptual similarity patterns. The perceptual assimilation of NG vowels to native AE vowel categories by AE listeners with no German language experience was then assessed directly. Both studies showed that acoustic similarity of AE and NG vowels did not always predict perceptual similarity, especially for "new" NG front rounded vowels and for "similar" NG front and back mid and mid-low vowels. Both acoustic and perceptual similarity of NG and AE vowels varied as a function of the prosodic context, although vowel duration differences did not affect perceptual assimilation patterns. When duration and spectral similarity were in conflict, AE listeners assimilated vowels on the basis of spectral similarity in both prosodic contexts.     

Theoretical Study on the Formation of H‐ and O‐Atoms,HONO, OH,NO, and NO2 from the Lowest Lying Singlet and Triplet States in Ortho‐Nitrophenol Photolysis

The photolysis of nitrophenols was proposed as a source of reactive radicals and NOx compounds in polluted air. The S₀ singlet ground state and T₁ first excited triplet state of nitrophenol were investigated to assess the energy dependence of the photofragmentation product distribution as a function of the reaction conditions, based on quantum chemical calculations at the G3SX//M06–2X/aug‐cc‐pVTZ level of theory combined with RRKM master equation calculations. On both potential energy surfaces, we find rapid isomerization with the aci‐nitrophenol isomer, as well as pathways forming NO, NO₂, OH, HONO, and H‐, and O‐atoms, extending earlier studies on the T₁ state and in agreement with available work on other nitroaromatics. We find that accessing the lowest photofragmentation channel from the S₀ ground state requires only 268 kJ/mol of activation energy, but at a pressure of 1 atm collisional energy loss dominates such that significant fragmentation only occurs at internal energies exceeding 550 kJ/mol, making this surface unimportant for atmospheric photolysis. Intersystem crossing to the T₁ triplet state leads more readily to fragmentation, with dissociation occurring at energies of ～450 kJ/mol above the singlet ground state even at 1 atm. The main product is found to be OH + nitrosophenoxy, followed by formation of hydroxyphenoxy + NO and phenyloxyl + HONO. The predictions are compared against available experimental data.     

The structure and helicity of perfluorooctanonitrile, CF3–(CF2)6–CN

New molecular structural data is presented for a cyanide terminated oligomer of polytetrafluoroethene. The target molecule, CF₃–(CF₂)₆–CN, has been seeded within a pulsed supersonic expansion of argon. The result of this action is to cool the species to rotational temperatures below 4 K. Within this state, the pure rotational spectrum of the oligomer has been recorded using two types of Fourier transform microwave spectroscopy. A total of 111 transitions have been identified involving rotational J levels between 6 and 40. Only a- and b-type transitions were observed. The spectrum has been analyzed using a Hamiltonian containing all three rotational constants and one centrifugal distortion constant, D_J. The experimental spectroscopic constants have been used to develop an effective molecular structure by scaling the quantum chemical calculated structure. The data shows that the seven carbon perfluorinated chain for the isolated oligomer twists ≈104°. This compares well to the C₇F₁₃-twist of ≈97° anticipated from the X-ray structure of phase II polytetrafluoroethene.     

High-resolution spectroscopy on trapped molecular ions in rotating electric fields: A new approach for measuring the electron electric dipole moment

High-resolution molecular spectroscopy is a sensitive probe for violations of fundamental symmetries. Symmetry violation searches often require, or are enhanced by, the application of an electric field to the system under investigation. This typically precludes the study of molecular ions due to their inherent acceleration under these conditions. Circumventing this problem would be of great benefit to the high-resolution molecular spectroscopy community since ions allow for simple trapping and long interrogation times, two desirable qualities for precision measurements. Our proposed solution is to apply an electric field that rotates at radio frequencies. We discuss considerations for experimental design as well as challenges in performing precision spectroscopic measurements in rapidly time-varying electric fields. Ongoing molecular spectroscopy work that could benefit from our approach is summarized. In particular, we detail how spectroscopy on a trapped diatomic molecular ion with a ground or metastable ³Δ₁ level could prove to be a sensitive probe for a permanent electron electric dipole moment (eEDM).     

Stress dependence of the domain wall dynamics in the adiabatic regime

In this work, we determine the domain wall velocity in the low field region and study the domain dynamics in as-cast and annealed bi-stable amorphous glass-covered Fe_77.5Si_7.5B₁₅ microwires. In particular, from the relation between the domain wall velocity and magnetic field in the adiabatic regime, the power-law critical exponent β, the critical field H₀ and the domain wall damping η were obtained. It has been verified that the main source of domain wall damping is the eddy current and spin relaxation, both with a strong relation with the magnetoelastic energy. This energy term is changed by the axial applied stress, which, by its time, modifies the damping mechanisms. It was also verified that the domain wall damping terms present different behavior at low (mainly eddy currents) and high applied stress (spin relaxation).     

The 12C(18O, α)26Mg and 12C(18O, 8Be)22Ne reaction

Excitation functions for α-emission leading to the ground and first excited states of ²⁶Mg and ⁸Be emission leading to the ground and first and second excited states of ²²Ne have been measured at several forward angles for E_c.m. = 15 to 22.4 MeV. There is little evidence for correlated structure. The angular distribution at 16.5 MeV for the α + ²⁶Mg(g.s.) channel is rather structureless while that for the ⁸Be+²²Ne(g.s.) channel appears to be dominated by a J = 13 contribution. Statistical model calculations indicate that much of the yield for both the α and ⁸Be exit channel is compound nuclear in origin, with some indication of a larger direct contribution for the ⁸Be channel at the lower end of the bombarding energy range.