Electron-nuclear-double-resonance of the VAl center in MgO

An ENDOR study of a hole center in MgO with g_|=2.0032±0.0001 and g_⊥=2.0385±0.0001 reveals that the hole interacts with an axial aluminum ion with A_⊥=±0.178±0.008 MHz, A_⊥=±0.074±0.008 MHz, and P= ±0.366±0.002 MHz. The structure of the center is consistent with the label, V_Al. It is suggested that the V_Al center may have been mistaken in the past for the V^- center because of the similarity of their g-values, method of production, and thermal properties.     

Determination of the kinetic parameters of the isomerization reaction of ethyl isocyanide using HeI photoelectron spectroscopy

The use of HeI photoelectron spectroscopy (PES) for the kinetic study of chemical reactions was introduced previously by us. As another example of the determination of the kinetic parameters of a chemical reaction using the PES method, the isomerization reaction of ethyl isocyanide CH₃CH₂NC → CH₃CH₂CN is investigated. It is found to be first order and the kinetic equations at 193.6, 200.0 and 210.3°C can be expressed as ln R_{466.6 K} = − (7.600 ± 0.026) × 10⁻⁵t − 0.4350; ln R_{473.0 K} = − (1.329 ± 0.032) × 10⁻⁴ − 0.4375 and ln R_{483.3 K} = − (3.170 ± 0.052) × 10⁻⁴ − 0.4354, respectively. The rate constants of the reactions at 193.6, 200.0 reactions at 193.6, 200.0 and 210.3°C are respectively (7.600 ± 0.026) × 10⁻⁵, (1.329 ± 0.032) × 10⁻⁴ and (3.170 ± 0.052) × 10⁻⁴ s⁻¹. The calculated activation energy (E_a) of this isomerization reaction is 38.36 ± 0.32 kcal mol⁻¹. These results are also in excellent agreement with the results obtained by a traditional method. This means that PES is a valuable method for determining the kinetic parameters of chemical reactions. The value of the intercept in the kinetic equations is related to the logarithm of the ratio of the photoionization cross-section of the bands used. This also means that the relative photoionization cross-sections of the bands used for the sample studied are obtained in the kinetic study of a chemical reaction using the PES method.     

Messung des Asymmetrie-Koeffizienten der β-γ-Zirkularpolarisationskorrelation an erlaubten β-Übergängen

The asymmetry coefficient of theβ-circularly-polarizedγ-correlation of allowedβ-decays has been measured for several nuclides with high accuracy. The polarimeter was a new type. Here the magnet is used as Compton-scatterer and asβ-spectrometer at the same time with the advantage that one has four coincidence possibilities between twoγ- and twoβ-counters. The results of the measurements are the following: NuclidA Na²⁴ +0.102±0.006 Ar⁴¹ +0.066±0.025 Sc⁴⁶ +0.103±0.004 Ca⁴⁷ +0.383±0.018 V⁴⁸ ?0.059±0.010 Mn⁵² ?0.019±0.010 Co⁵⁶ +0.002±0.010 Co⁵⁹ ?0.106±0.023 Ag^110m +0.058±0.007 Cs¹³⁴ ?0.069±0.007 Fermi matrix elements are determined from these values and their physical implications are discussed.     

Pion electromagnetic polarizabilities and quarks

The electric and magnetic polarizabilities of the neutral and changed pion are calculated in a coloured quark field theory at the one-loop level. The theory has as free parameter the quark mass but our results do not depend on it. We have found that the electric polarizabilities are α_π^±=?0.04α/m_π³, α_π0=?0.4 α/m_π³. These values are compared with calculations in other models and some comments are made about the polarizability sum rules.     

Magnetic HFI of cerium in an iron garnet investigated by angular correlations

The magnetic HFI of cerium ion in a lanthanum-doped yttrium iron garnet is investigated by the gamma-gamma angular correlation technique. It is found that cerium, formed after radioactive decay of La¹⁴⁰, reaches the ground state of Ce³⁺ in a time short compared with the nuclear state life-time of 4.9 nsec. Quasi-static as well as time-dependent interactions are detected, yielding an internal field ofH _eff=(21.5± 3) kOe at the nuclei of cerium. The molecular field theory is applied in the analysis of data, and values for the exchange field, the spinlattice relaxation time and the magnectic moment of cerium ion in an iron garnet at room temperature are deduced. These values are:H _exch=(147±20)kOe, τ _c =(4.5±0.6)×10^?13 sec and 〈μ_z〉=(0.017±0.002) Bohr magnetons.     

Investigation of gamma ray transitions and lifetimes in35Cl

Fortyeight resonances of the³⁴S(p, γ)³⁵Cl reaction in the proton rangeE _p=1–2 MeV have been observed. Gamma decay of twentyeight of these was investigated by means of a 55 cm³ Ge(Li) detector, and the energies and branching ratios of several bound states have been determined. TheQ-value was found to be 6367.0 ± 1.5 keV. The lifetimes 150±20, 400±140, 19±4, 14±2, 145±50, 20±5, 20±4, 42±4 and 7±3 fs were determined with the DSA method for the states at 1219, 1763, 2694, 3003, 3944, 3967, 4059, 4178 and 4882 keV, respectively. The experimental transition strengths were found to be in agreement with those given by manyparticle shell-modell calculations.     

Infrared diode-laser spectrum of the CH3CN ν2 band: Analysis of local resonances with ν6±1 + 2ν8±2, ν4 + ν7±1 + ν8±1, ν4 + ν6±1, ν4 + ν7±1, and 2ν70 + ν8±1 states

Fifty-one sections of infrared diode-laser spectra of acetonitrile have been measured in the region from 2283.5 to 2235.7 cm^?1. About 450 transitions belonging to the ν₂ band have been assigned for K ≦ 7 and J ≦ 44. Anomalies found in the rotational structure have been proven to be due to five local resonances. Observed transition frequencies have been fitted by a least-squares method to a model which includes Fermi-type resonances (Δk = 0, Δ? = ± 3n) with ν₆^±1 + 2ν₈^±2 and ν₄ + ν₇^±1 + ν₈^±1 states, x, y-type Coriolis resonances (Δk = ±1, Δ? = ?3n ± 1) with ν₄ + ν₆^±1 and ν₄ + ν₇^±1 + ν₈^±1 states, and a centrifugal-distortion-type resonance (Δk = ±2, Δ? = ?3n ± 2) with a 2ν₇⁰ + ν₈^±1 state. The 11 × 11 dimensional energy matrix has been diagonalized in order to obtain the perturbed energy levels. The standard deviation for the fit is 1.075 × 10^?3 cm^?1. The molecular constants determined are also listed.     

γ-Detected NMR of103 mRhFe

Using the method ofγ-detection, the NMR in the metastable 40 keV-state of¹⁰³Rh in Fe (thin foils with diffused¹⁰³Pd activity) was measured in external fields of 0.5 to 14 kG. We find a zero-field resonance frequency ofv ₀=(550.3±0.5) MHz and a slope ofdv/dH= ?(0.933 ±0.017) MHz/kG, yielding g=1.22 ± 0.02. The resulting value for the hyperfine field, H_hf=(590±10) kG, is inconsistent with that of an NMR measurement in the ground state of¹⁰³Rh. Possible reasons for this discrepancy are discussed.     

The S34 (p, γ) Cl35 reaction and energy levels of the Cl35 nucleus

A method is presented to eliminate quantitatively the decay time of the radioactive source and all systematic errors caused by the instability of the associated electronics. The essential part of this procedure is a versatile method to measure the random coincidences together with the sum of true and random coincidences under the same experimental conditions for both quantities. The proposed method is applied toγ-γ-directional correlation measurements with a five detector apparatus. The construction and function of the device is illustrated. Test measurements with⁶⁰Co prove the usefulness of the method and the capability of the apparatus. The investigation of twoγ-γ-cascades in the decay of¹²⁴Sb gives the following values for the coefficients of the correlation function 1,69-0,603 MeV-cascade:A ₂=?0,065±0,003A ₄=+0,001±0,005 2,09-0,603 MeV-cascade:A ₂=?0,056±0,008A ₄=+ 0,006±0,008     

Lifetimes and magnetic moments of two states in62Cu

The lifetimes and the magnetic moments of the two excited⁶²Cu states at 40.84 and 390.19 keV are investigated by time differential perturbed angular distribution measurements of the delayedγ-rays following the nuclear reactions⁶¹Ni(d, n) and⁶²Ni(p, n). The results are:τ=6.7±0.5 nsec,μ=1.32±0.03 n. m. for the 2⁺ state at 40.84 keV, andτ=16.0±0.3 nsec,μ=2.00±0.01 n. m. for the 3⁺ state at 390.19 keV.     

Lifetime measurements of lithiumD-states

We report lifetime measurements of the 1s ² 3d ² D, 1s ²4d ² D, and 1s ²2p ² P states of lithium. The results τ=14.5±0.7 ns, τ=31.0±1.0 ns, and τ=27.9±1.0 ns respectively were obtained by time resolved detection of the resonance fluorescence following pulsed laser excitation.     

Recoil distance lifetime measurements in 26Mg and 26Al

Levels in ²⁶Mg and ²⁶Al were excited with the ²³Na + α reaction, and the recoil-distance method was used to determine the mean lives of the following levels: ²⁶Mg, 3.59 MeV (9.6 ± 1.2ps) and 3.94 MeV (1.38 ± 0.11 ps); ²⁶Al, 1.76 MeV (6.4 ± 0.4 ps) and 2.072 MeV (1.00 ± 0.10ps). The deduced values are compared to previous measurements by the Doppler-shift attenuation method.     

Slow neutron scattering lengths of the isotopes of silver and indium

By means of the Cristiansen filter method we measured on filters containing powder, filings or wires of silver or powder of indium oxide the coherent scattering lengths for the bound atoms of the following isotopes:b(¹⁰⁷Ag)=7.64±0.04 fm,b(¹⁰⁹Ag)=4.19±0.03 fmb(nat.Ag)=5.97±0.01 fm,b(¹¹³In)=5.39±0.06 fmb(¹¹⁵In)=4.00±0.03 fm andb(nat.In)=4.065±0.020 fm. From these values and taking account of incoherent and resonance data we deduced values for the fundamental spin state scattering lengths and incoherent cross sections. These zero energy scattering parameters and the resonance parameters for silver are consistent if bound levels of¹⁰⁸Ag and¹¹⁰Ag are assumed. No indications were found for bound levels of the In isotopes.     

Messung der Winkelverteilung der Neutronenpolarisation bei Streuung von 15,85 MeV-Neutronen am Kohlenstoff

AtE _n=15.85 MeV the angular distributions of neutron polarizationP(θ) for¹²C(n, n)¹²C and of scattering asymmetry A(θ) for¹² C(n,n′)¹² C ^*(Q=?4.43 MeV) have been measured. In a neutron time-of-flight method with a plastic scintillator as scatterer carbon recoil nuclei were used for detection. Polarized neutrons were produced in thed-t reaction atE _d=1.90 MeV at a reaction angle of 70° (lab.). WithP _n=?0.135 scattering polarizations P(θ) are forθ _lab=30, 40, 50, 60, 70, and 80° respectively ?27.0±2.1, ?48.4±2.7, ?68.7±3.6, ?20.7±6.2, +5.3±3.9, and +2.1±4.5%.     

Static moments of 54Fem and perturbed angular distributions with combined dipole and quadrupole interactions

The static moments of a new I^π = (10⁺) isomer in ⁵⁴Fe (E_x = 6528keV; τ = 525 ± 10ns) were measured by the perturbed angular distribution method with the results g = +0.778 ± 0.010, |Q| = 72 ± 7efm². The isomer was then used to study the combined interaction produced by weak randomly-oriented electric field gradients in the presence of a strong magnetic field.     

E2 transition probabilities in77Br

⁷⁷Br has been investigated by the reaction⁶⁴Ni(¹⁶O,p2nγ) at 60 MeV. The following mean lives (in parentheses) have been determined by the recoil distance Doppler shift method (energies in keV): 161.9 (718±50 ps), 575.2 (14.2±2.1 ps), 639.0 (14.1±0.8 ps), 782.0 (4.3±0.9 ps), 790.1 (6.2±0.8 ps), 1,273.2 (4.0±1.0 ps), 1,303.0 (4.0±1 ps), 1,480.8 (0.6 ±0.2 ps). The resultingB(E2) values are compared with rotor plus particle calculations. Nuclear reaction⁶⁴Ni(¹⁶O,p2nγ)E ₀=60 MeV; measuredE _γ, recoil distance Doppler shift; deducedT _1/2. Enriched target, Ge(Li).     

Reinvestigation of the quadrupole hyperfine structure in rotational spectra of chloroiodomethane

The b-type Q-branch transitions of chloroiodomethane were remeasured and the quadrupole hyperfine structures were reinvestigated by a new method to improve the discrepancies in the hyperfine spectra observed and calculated in a previous work. The χ values of the off-diagonal element of ³⁵Cl and ³⁷Cl were determined. The nuclear quadrupole coupling constants were revised to be χ_aa = −1421.9 ± 1.9, χ_bb = 392.6 ± 1.0, χ_cc = 1029.3 ± 2.1, and {χ_ab} = 1174.9 ± 1.7 MHz of iodine; χ_aa = −31.1 ± 1.1, χ_bb = −9.0 ± 0.6, χ_cc = 40.1 ± 1.2, and {χ_ab} = 53.6 ± 4.2 MHz of ³⁵Cl for ³⁵Cl species; χ_aa = −1418.4 ± 2.5, χ_bb = 386.5 ± 2.7, χ_cc = 1031.9 ± 3.6, and {χ_ab} = 1181.8 ± 1.7 MHz of iodine; and χ_aa = −21.1 ± 1.7, χ_bb = −8.5 ± 0.9, χ_cc = 29.6 ± 1.9, and {χ_ab} = 34.6 ± 1.4 MHz of ³⁷Cl for ³⁷Cl species, respectively.     

The reaction 36(α, γ)40Ar: γ-transition properties of resonance and bound states in 40Ar

The El character of the de-excitation of the 9 to 10 MeV states in ⁴⁰Ar has been studied through the reaction ³⁶S(α, γ)⁴⁰Ar. Angular distributions and γ-yield asymmetries of primary transitions from the E_α = 2.35 to 3.50 MeV resonances have been measured. The Doppler-shift attenuation method was used to obtain the following lifetime values: 720 ± 120fs (E_x= 2.52 MeV), 89 ±17 (3.21), 90±17(3.511), 22 ±9 (4.33), and 105 ± 17 (4.60).     

The beta branching ratio and conversion coefficients in the137Cs decay

The decay of¹³⁷Cs has been reinvestigated using several precision counting methods. The emission rate ofβ-particles plus internal conversion electrons was measured by the 4π-proportional counter method using vacuum evaporated sources free of self-absorption and checked by the liquid scintillation method. TheK-conversion coefficient was determined by the electron X-ray coincidence method using a magnetic spectrometer and a high resolution Si(Li) detector. TheK/(L+M+...) conversion ratio and a second less accurate value for the β-branching ratio were obtained from the recorded electron spectra. Theγ-ray emission rate of all sources was determined to within ±0.14%, on the average, with a calibrated NaI(Tl) crystal detector. As results the intensity of theβ-decay to the ground state of¹³⁷Ba could be determined to (5.4±0.3)% of the¹³⁷Cs decays, theK-conversion coefficient to 0.0916±0.0004, and theK/(L+M+...) conversion ratio to 4.41±0.04. From these values the γ-ray emission intensity is (85.1±0.4)% of the¹³⁷Cs decays and theK X-ray emission intensity is (8.13±0.10)% of the emittedγ-rays. All errors are discussed in detail.