Spin and orbital contributions to collective M1 transitions in 46,48Ti

Low- and high-lying K^π = 1⁺ states and M1 transitions in ^46,48Ti are studied. The model hamiltonian is treated in the quasi-particle particle random phase approximation (QRPA) with an exact restoration of its rotational invariance. A considerable spin contribution to the transition matrix elements is found for the low-energy (about 4 MeV) strong M1 transition (the orbital contribution being 30–70% of the spin one), although the microscopic structure of this state in ⁴⁶Ti is typical for an orbital isovector excitation. The calculated energies and B(M1) values are in good agreement with the experimental data. The results are compared to the estimates of the isovector scissor model.     

Level density parameters of47Ti and50V

The energy distribution of the protons andα-particles from the reactions⁴⁷Ti(α, α′),⁴⁷Ti(α, p) and⁵⁰V(p, α) was measured in the angular range from 60° to 150°. The energies of the incoming particles were 15.35 MeV forα-particles and 13.85 MeV for protons. The results can be described in the frame of the statistical model of the nuclear reactions. The level density parameters could be determined by comparing the experimental data with the theoretical results. The values for the backshifted Fermi gas model are⁴⁷Ti:a=6.6±0.6MeV^?1,Δ=?0.5±0.3 MeV⁵⁰V:a=6.3±0.6 MeV^?1,Δ=?1.0±0.3 MeV.     

Cation site environment in ultrathin TiOx films grown on Pt(1 1 1) probed by X-ray absorption spectroscopy at the Ti 2p edge

We present the results of a XAS experiment carried out at the Ti 2p edge on well-ordered TiO_x ultrathin films grown on the Pt(1 1 1) surface. XAS at the Ti 2p edge has been extensively applied to the study of Ti bulk compounds, particularly to the study of titania. According to the literature, the corresponding Ti 2p edge spectral shape is related to the stoichiometry and crystal field symmetry at the Ti sites. In the present study we aim at extending the potential of the XAS technique by discussing Ti 2p spectra obtained on several, dimensionally confined, TiO_x phases in the form of ultrathin films. One of the main features of these films is their high degree of structural order. Furthermore, the results of previous studies provide valuable information about the chemistry and structure of the films, so that we are able to analyse the current XAS data in detail and to compare them with the appropriate Ti 2p XAS data of bulk oxides. We find that in the case of ultrathin film with a fully oxidised Ti⁴⁺ stoichiometry, the Ti 2p XAS data display features that are very similar to the ones observed in related bulk systems. The XAS data of the reduced TiO_x films (with x < 2) show a rather different and specific shape. By comparing the experimental spectra with an atomic type of model calculation we show that the Ti 2p XAS profiles can be attributed mainly to stoichiometry-symmetry effects.     

Electroexcitation of magnetic dipole and other modes in46Ti and48Ti

With high-resolution inelastic electron scattering measurements on⁴⁶Ti and⁴⁸Ti the excitation mechanism of the transition into low lying J^π=1⁺ states is investigated. The experimental evidence of considerable contribution of the orbital part of theM1 operator to the total transition strength is given by a model dependent analysis of form factors. The possibility of physical relationship to low lying J^π=1⁺ states in the rare earth nuclei is discussed in various models. MoreoverE2 form factors and good candidates forM3 form factors are presented.     

Isotope Shifts in the TiO B-X (1-0) Band

The absorption spectrum of the B³Π-X³Δ (1-0) band of the TiO molecule has been studied at sub-Doppler resolution by crossing an effusive beam of TiO with a cw tunable laser beam and by collecting the induced fluorescence light. The five bands involving the ⁴⁶Ti, ⁴⁷Ti, ⁴⁸Ti, ⁴⁹Ti, and ⁵⁰Ti isotopic species have been observed and interpreted. A simultaneous analysis of the five isotopic data leads to accurate molecular constants and energy levels for the B³Π electronic state.     

Microscopic description of the E1 resonance in titanium isotopes

The structure of the dipole resonance in even-even isotopes of titanium is calculated within the particle-core coupling (PCC) version of the shell model using data from spectroscopy of direct (p, d) reactions. The main features of the E1 resonances in ⁴⁶Ti, ⁴⁸Ti, and ⁵⁰Ti are reproduced.     

Lepton flavor violation: Constraints from the exotic μ−-eμ− conversion

The exotic neutrinoless μ^? → e ^? conversion is studied within conventional extensions of the standard model as well as in minimal supersymmetric models with R-parity-conserving and R-parity-violating mechanisms. The dependence on the nucleon and nuclear structure of the μ-e conversion rates is consistently taken into account. From the available experimental data on the branching ratio $R_{\mu e^ - }$ for the currently interesting nuclei ⁴⁸Ti and ²⁰⁸Pb, and from the experimental sensitivity for ²⁷Al, which has been employed as a target in MECO experiment at Brookhaven, we extract very severe constraints for the flavor violation parameters with our calculated transition matrix elements. We especially emphasize the constraints resulting for SUSY R-parity-violating parameters.     

K-shell ionization of Si,Ti, Cu and Ag for incident protons,4He and14N ions in the energy range of 0.17–2.0 MeV/amu

K-shell X-ray production cross sections of Si, Ti, Cu and Ag were measured for incident protons,⁴He and¹⁴N ions in the energy range of 0.17≦E ₁/A ₁≦2 MeV/amu. The experimental ionization cross sections are compared with calculations according to the simple Plane Wave Born Approximation (PWBA) theory as well as the corrected PWBA model (PWBABC). Strong deviations of the experimental cross sections from theZ ₂ ¹ scaling are observed and discussed quantitatively.     

The effect of an electromagnetic wave-field pressure on the propagation of slow tm waves along the plasma layer

Angular distributions of the⁴⁸Ti(d, t)⁴⁷Ti and⁴⁷Ti(d, t)⁴⁶Ti reactions have been measured atE _d =19.5 MeV and analyzed by DWBA. The data suggest an explanation of the⁴⁸Ti(d, t)⁴⁷Ti ground state transition by means of a [f ₇ ^2/5 ·f _5/2]₀₊ neutron component in the ground state of⁴⁸Ti.     

Energy distribution of the <Emphasis Type="Italic">E</Emphasis>1-transition strengths in the <Superscript>46</Superscript>Ti nucleus

The structure of levels of the ⁴⁶Ti nucleus is studied by means of the nonselective reaction ⁴⁵Sc(p, γ) at proton energies ranging between 1.2 and 3.1 MeV. Spin-parity assignments for ⁴⁶Ti states of excitation energies up to 5.5 MeV are obtained by using the method of averaged resonances. Radiative strength functions for E1 transitions populating these states are determined. The resulting data are compared with predictions of various models.     

Decays of T Z = − 3/2 nuclei 23Al, 31Cl, and 41Ti

This article gives an overview on the decay spectroscopy of T _Z ?=???3/2 nuclei ²³Al, ³¹Cl, and ⁴¹Ti performed at the Ion Guide Isotope Separator On-Line (IGISOL) facility. The results of the IGISOL experiments are compared to the experimental results that have been published since. The isobaric multiplet mass equation (IMME) has been studied for the T?=?3/2 quartets at A?=?23 and A?=?31. For ⁴¹Ti, a detailed comparison to the Gamow–Teller strengths obtained for the analog transitions via charge-exchange reactions has been done. Further improvements in the experimental instrumentation and methods and possible implementations for studying T _Z ?=???3/2 nuclei at the new IGISOL facility are discussed.     

N incorporation and electronic structure in N-doped TiO2(1 1 0) rutile

We describe the growth and properties of well-defined epitaxial TiO_2−xN_x rutile for the first time. A mixed beam of atomic N and O radicals was prepared in an electron cyclotron resonance plasma source and Ti was supplied from a high-temperature effusion cell or an electron beam evaporator, depending on the required flux. A very high degree of structural quality is generally observed for films grown under optimized anion-rich conditions. N substitutes for O in the lattice, but only at the ∼1 at.% level, and is present as N³⁻. Epitaxial growth of TiO₂ and TiO_2−xN_x rutile prepared under anion-rich conditions is accompanied by Ti indiffusion, leading to interstitial Ti (Ti_i), which is a shallow donor in rutile. Our data strongly suggest that Ti_i donor electrons compensate holes associated with substitutional N²⁻ (i.e., Ti(III) + N²⁻ → Ti(IV) + N³⁻), leading to highly resistive or weakly n-type, but not p-type material. Ti 2p core-level line shape analysis reveals hybridization of N and Ti, as expected for substitutional N. Ti-N hybridized states fall in the gap just above the VBM, and extend the optical absorption well into the visible.     

The46Ti(d,τ)45Sc reaction

The⁴⁶Ti(d, τ)⁴⁵Sc reaction has been investigated at an incident energy of 52 MeV. Angular distributions have been taken for 14 τ-groups corresponding to excitation energies below 4 MeV in⁴⁵Sc. Spectroscopic factors were extracted through DWBA calculations. Spins and parities of 5/2⁺ are proposed for states at 1.30, 1.80, 2.91, 3.48, and 3.72 MeV. The hole state spectrum of⁴⁵Sc closely resembles that of⁴⁷Sc. A strong fractionation of the 1d _3/2 strength was not observed in contrast to other recent work. The data provide evidence for (1f _7/2 · 1f _5/2 ¹) components in the ground state wave function of⁴⁶Ti, which demonstrates that such configurations are not restricted to neutron excitations.     

Q-value of the 40Ca(α, γ)44Ti reaction

The Q-value of the ⁴⁰Ca(α, γ)⁴⁴Ti reaction has been measured by comparing resonance α-particle and γ-ray energies to those of the prominent $\text{T =}\text{3}\text{2}$ resonance in the ¹⁵N(α, γ)¹⁹F reaction, for which the Q-value is known with an accuracy of 0.12 keV. The result for the ⁴⁰Ca(α, γ)⁴⁴Ti reaction is Q = 5127.1 ± 0.7 keV. It follows that the mass excess of ⁴⁴Ti is ?37549 ± 1 keV.     

Resonances in low energy40Ca(α, α)-scattering and quasimolecular band in44Ti

The elasticα-scattering from⁴⁰Ca has been studied betweenE _α=7.035 MeV and 7.405 MeV. Angular distributions and excitation functions have been measured in 5 keV steps. The data display a resonance atE _α=7.26 MeV which by its width and angular correlation is clearly distinguished from strong Ericson fluctuations in this region. From the analysis of the angular distributions and excitation functions a spinJ ^π=1^? is assigned to this resonance. The resonance parameters areΓ _α=31 KeV,Γ _total=51keV. By its spin and excitation energy this state is interpreted as a member of a quasimolecular band in⁴⁴Ti the higherl-members of which are known from⁴⁰¹Ca(α, α) scattering betweenE _α=18 MeV and 50 MeV. The experimental data are compared with recent microscopic calculations within a fully antisymmetrized reaction theory.     

A shell-model study ofA=48–52 nuclei and magnetic strength distributions in50Ti

An extensive shell-model calculation has been performed on fivefp-shell nuclei in the mass regionA = 48–52. The model space, which includes 1p-1h excitations, reproduces the experimental spectra very well except for the 0 ₂ ⁺ state in⁵⁰Ti. It is demonstrated that the 0 ₂ ⁺ state can be reproduced by a model space which also includes 2p-2h excitations. Strong neutronp-h components in the wave functions of states in ₂₂ ⁵⁰ Ti₂₈ are found despite the closure of the neutron f_7/2 orbit. Magnetic transitions in⁵⁰Ti are discussed, and in contrast to the 1p-1h results a sufficiently large quenching ofB(M1) strengths in the 2p-2h model space is found. Effects of 2p-2h admixtures onM 5 transition strengths are discussed as well.     

Beta decays of 44V and 52Co

We have studied the prevously unknown β⁺ decay branches from ^44,44mV and ⁵²Co to particle-bound states in ⁴⁴Ti and ⁵²Fe, respectively. These intense branches populate a few states in the daughters from an excitation energy of about 1 MeV up to the isobaric analogue states at about 6 MeV. We have measured the first precise energy values for the latter states as well as the β-branching ratios to all states in this excitation energy region. We have calculated the β⁺ decay of ^44,44mV in the full fp shell model space as well as in a truncated space. Renormalized transition operators are constructed for the truncated space and tested against experimental data in ⁴⁴V and ⁵²Co. In general there is good agreement between theory and experiment for the half-lives, level energies and beta branches, but not all the states found are reproduced by the calculations.     

High resolution study of the 6ν1 P-H stretching band of the PHD2 molecule

The high resolution spectrum of a phosphine gas mixture containing PHD₂ was recorded at room temperature in the 12 550-12 770 cm⁻¹ region. A high sensitivity laser photoacoustic spectrometer consisting of a longitudinal resonant cell coupled to a Ti:sapphire ring laser was employed. More than 600 transitions were assigned to the 6ν₁ overtone band of PHD₂ up to J^max=20, K_a^max=6. A Hamiltonian model developed up to the octic centrifugal distortion terms was used. Seven rotational and centrifugal distortion parameters were fitted, the other ones being fixed to their values linearly extrapolated from ν₁ and 2ν₁. The derived parameters reproduce the initial data within the experimental uncertainties. The isolated character of the P-H bond is confirmed.