Theg-factor of the 659 keV level in117In

We have measured theg-factor of the 659 keV, 3/2⁺, state in¹¹⁷In, using time differential perturbed angular correlation technique. The spin precession of this state was measured in an external field of 20·2 kG. The values of the Larmor precession frequencyω and theg-factor are obtained to be (60·1±0·3)10⁶ rads/sec and 0·625±0·007 respectively.     

Das gyromagnetische Verhältnis des 137 keV Rotationsniveaus von Os185

The rotation of the angular correlation of the 631 keV-137keVγ-γ-cascade in the decay of Re¹⁸⁶ in an external magnetic field of 53 500 gauß was determined to:ωτ=0·098 ± 0·008. The half life of the 137 keV level was measured as: T_1/2=(0·84 ± 0·03) · 10^?9 sec. The coincidences between the 137 keVγ-radiation and theβ-group of 927 keV maximum energy were used in connexion with a time to pulse height converter circuit. The coefficients of the angular correlation of the 631 keV-137 keV γ-γ-cascade were found as: A₂=? 0·073 ± 0·010; A₄=+ 0·310 ± 0·014. These values imply corrections for 3·9% admixture of internal bremsstrahlung and a 1 % contribution by K-X-radiation. The solid angle-corrections were done according to the formula given by E.Rose. The comparison with the theoretical coefficients for a (2⁺ 2⁺ 0⁺)-cascade shows that the multipolarity of the 631 keV radiation is pure E₂, the M₁ admixture being less than 0· 1%. This result is in agreement with the K-selection rule. There is no appreciable attenuation by internal fields. The comparison with the theoretical angular correlation gives for the integral attenuation factor: G₄=0·95±0·04; Assuming only attenuation by electric quadrupole interaction one gets for: G₂=0·92±0·07; The nuclear g-factor of the 137 keV rotational state was derived from these results without any further correction as: g_R= + 0·316±0·028.     

Uniqueness of the standard model neutral current predictions

In view of an excellent agreement between the recently determinedv _μ-hadron couplings and predictions of the standard model, the basic question discussed is how far its neutral current predictions can be mimiced in going either from the isodoublet to an isotriplet (or an even higher isospin) left-handed representation or from SU _L (2) × U(1) toG × U(1), whereG is a simple group of rank two. This question is addressed with reference to a sufficiently broad class of schemes. Their most distinctive properties are: in the higher isospin scheme, neutrino couplings are precisely in the form obtainable with standard l.h. representation; the higher g.g. scheme isL+R type in which, to each light fermion of evenRU parity, a superheavy fermion of the same charge and oddRU parity is associated, parity conservation forbidding their mixing. Reasons for excluding theL-type andG ₂ higher g.g. schemes are given. Their neutral current predictions are compared with those of the standard model. A higher isospin representation can mimic the predictions of the standard model in inclusive and semi-inclusivev _μ-hadron reactions but is conclusively discriminated from the isodoublet representation by elasticv _μ ⁽⁻ p scattering. TheG × U(1) scheme can mimic standard model neutrino sector but is conclusively discriminated from minimal scheme by parity violating effects.     

Does the G·G*syn DNA mismatch containing canonical and rare tautomers of the guanine tautomerise through the DPT? A QM/QTAIM microstructural study

We have established that the asynchronous concerted double proton transfer (DPT), moving with a time gap and without stable intermediates, is the underlying mechanism for the tautomerisation of the G·G^*_syn DNA base mispair (C₁ symmetry), formed by the keto and enol tautomers of the guanine in the anti- and syn-configurations, into the G^*·G^*_syn base mispair (C₁), formed by the enol and imino tautomers of the G base, using quantum-mechanical calculations and Bader's quantum theory of atoms in molecules. By constructing the sweeps of the geometric, electron-topological, energetic, polar and natural bond orbital properties along the intrinsic reaction coordinate of the G·G^*_syn?G^*·G^*_syn DPT tautomerisation, the nine key points, that are critical for the atomistic understanding of the tautomerisation reaction, were set and comprehensively analysed. It was found that the G·G^*_syn mismatch possesses pairing scheme with the formation of the O6···HO6 (7.01) and N1H···N7 (6.77) H-bonds, whereas the G^*·G^*_syn mismatch – of the O6H···O6 (10.68) and N1···HN7 (9.59 kcal mol^?1) H-bonds. Our results highlight that these H-bonds are significantly cooperative and mutually reinforce each other in both mismatches. The deformation energy necessary to apply for the G·G^*_syn base mispair to acquire the Watson–Crick sizes has been calculated. We have shown that the thermodynamically stable G^*·G^*_syn base mispair is dynamically unstable structure with a lifetime of 4.1 × 10^?15 s and any of its six low-lying intermolecular vibrations can develop during this period of time. These data exclude the possibility to change the tautomeric status of the bases under the dissociation of the G·G^*_syn mispair into the monomers during DNA replication. Finally, it has been made an attempt to draw from the physico-chemical properties of all four incorrect purine–purine DNA base pairs a general conclusion, which claims the role of the transversions in spontaneous point mutagenesis.     

Determination of the gravitational constant G

A precise knowledge of the Newtonian gravitational constant G has an important role in physics and is of considerable meteorological interest. Although G was the first physical constant to be introduced and measured in the history of science, it is still the least precisely determined of all the fundamental constants of nature. The 2002 CODATA recommended value for G, G = (6.6742 ± 0.0010) × 10⁻¹¹m³ · kg⁻¹ · s⁻², has an uncertainty of 150 parts per million (ppm), much larger than that of all other fundamental constants. Reviewed here is the status of our knowledge of the absolute value of G, methods for determining G, and recent high precision experiments for determining G.     

Spectroscopy properties of the amide group in valpromide and some derivatives with antiepileptic activity

Infrared spectra at 300 and 77 K and Raman spectra at 300 K of the valpromide (Vpd), N‐substituted derivatives, N‐ethylvalpromide (Etvpd), N‐isopropylvalpromide (Ipvpd) and the N,N‐disubstituted derivative, N,N‐dimethylvalpromide (Dmvpd) with antiepileptic activity, have been measured and analyzed with results derived from computational chemistry calculation. In agreement with theoretical predictions, experimental data indicate that while in Etvpd, Dmvpd and Ipvpd there are four different conformational co‐existing components (Etvpd: TTCG⁺, TCCG⁻, TTTC, G⁺G⁺C G⁺; Dmvpd: TTCC, G⁻TTA⁺, G⁺A⁻TC, G⁺A⁻C A⁺; Ipvpd: TTCT, TCCT, TCCC, G⁻ TTT) in the Vpd there are only three distinct stable conformations of C₁ symmetry group: TTC, TCT, G⁺G⁺T. Based on the accuracy of the B3LYP calculation, with the 6‐31 + G** basis set estimated by comparison between the predicted values of the vibrational modes and the available experimental data, we performed a structural and vibrational study of the amide group in the Vpd and their derivatives. We found that small nonplanarity deviations of C(O)N backbone induce significant changes on the structural and spectroscopic properties. These are not compatible with the decreasing of the resonance effect as it is produced when the twisting around the C(O) N increases. From the Natural Bond Orbital (NBO) analysis the existence of stabilizing electrostatic interactions of type C H···O/N and C H···H N/C, which induce significant structural changes and a complex electronic redistribution of charge on the π‐system in those structures becomes evident. We view this as a consequence of the filled electron density change Lewis‐type NBOs type lp_{O1, 2}, lp_N1, σ_{(C H)N acyl} and empty non‐Lewis NBOs type σ*_{(C H)N acyl}, σ*_{N H}. Copyright © 2009 John Wiley & Sons, Ltd.     

Zeeman spectroscopy of the 4 Eu → 2 B 1g phosphorescence of copper porphin in an n-alkane single crystal

The phosphorescence spectrum of the metastable ⁴ E_u state of copper porphin in single crystals of n-octane (C₈) and n-decane (C₁₀) has been studied between 2·3 and 35 K, with and without a magnetic field B. The crystal field splitting between the orbital components observed at 35 K is δ = 30·3 ± 0·3 (C₈), 13·8 ± 0·2 cm^-1 (C₁₀). From the Zeeman shifts we derive the effective orbital angular momentum Λ′ = 0·8 ± 0·2 (C₁₀), the spin-orbit coupling parameter |Z′| = 1·5 ± 1·0 cm^-1 (C₁₀), the spin-spin dipolar interaction parameters D = -0·1 ± 0·2 cm^-1 (C₈, C₁₀) and |E| = 0·31 ± 0·03 cm^-1 (C₈, C₁₀), and the g-factors g _∥ = 2·14 ± 0·04 (C₈, C₁₀) and g _⊥ = 2·00 ± 0·03 (C₈, C₁₀).     

Interference of Higgs boson resonances in $\mu^ + \mu^- \to\tilde{\chi}^0_i\tilde{\chi}^0_j$ with longitudinal beam polarization

We study the interference of resonant Higgs boson exchange in neutralino production in m⁺ m^-\mu^ + \mu^- annihilation with longitudinally polarized beams. We use the energy distribution of the decay lepton in the process [(c)\tilde]⁰_j ? l^± [(l)\tilde]^-±\tilde{\chi}^0_j \to \ell^{\pm} \tilde{\ell}^\mp to determine the polarization of the neutralinos. In the CP-conserving minimal supersymmetric standard model a non-vanishing asymmetry in the lepton energy spectrum is caused by the interference of Higgs boson exchange channels with different CP-eigenvalues. The contribution of this interference is large if the heavy neutral bosons H and A are nearly degenerate. We show that the asymmetry can be used to determine the couplings of the neutral Higgs bosons to the neutralinos. In particular, the asymmetry allows one to determine the relative phase of the couplings. We find large asymmetries and cross sections for a set of reference scenarios with nearly degenerate neutral Higgs bosons.     

Anharmonic force constants of GaSb from the measured third order elastic constants at 300°K

The third-order elastic constants of single crystal GaSb are determined using ultrasonic pulse interferometer at 10 MHz. The constants at 300°K, in units of 10¹¹ N.m.⁻², are C_l11 = ™ 4 ·75 ± 0·06 C₁₄₄ = + 0·50 ± 0·25 C₁₁₃ = ™ 3 ·08 ± 0·02 C₁₆₆ = ™ 2·16 ± 0·13 C₁₂₃ = ™ 0 ·44 ± 0·29 C₄₅₆ = ™ 0·25 ± 0·15 These constants are used to evaluate the three anharmonic first and second neighbour force constants based on modified Keating’s model. The constants are (in units of 10¹¹ N.m⁻²)γ=− 2·406;δ=0·407;ε=−0·222.     

Least squares adjustment of the coupling constants in nuclear beta-decay

Assuming theV-A theory, fully polarized neutrinos, and lepton conservation, best values of the vector and axial vector coupling constants are deduced from all available data on neutron decay and from theft- values of¹⁴O,^26mAl and³⁴C1. Special consideration is given to the treatment of errors and to radiative corrections. For the determination of the coupling constantratio, radiative corrections are, at present, unimportant. We find ¦G_A/G_V¦=1.250 + 0.009 with a phase angle φ=(181.1±1.3)⁰. From the weighted mean ?t-value, including charge dependent and “outer” radiative corrections, we find an effective coupling constant G′_V=(1.413±0.002)x 10⁴⁹erg cm³. The error is mainly due to the uncertainty of charge dependent corrections.     

Analysis of average primary gamma-transition intensities and cross sections of the113Cd(n, γ) reaction

A combined analysis of the available data on the primaryγ-ray intensities from the¹¹³Cd(n, γ) reaction atE _n=1.9 and 24.3 keV neutron energies together with the data on¹¹³Cd neutron capture cross sections in theE _n=3–200 keV energy region was carried out. The neutron strength functions were determined asS _n0=(0.260±0.073) 10^?4 and S_n1=(5.06±0.67) 10^?4. No spin-orbit splitting of thep-wave neutron strength function was found. The energy dependence of theE 1 radiative strength function {ie147-01} was fitted by the Kadmenski-Furman model somewhat better than by a standard Lorentzian. TheM 1 giant resonance parameters were obtained as E _G ^{M 1} =8.8±1.6 MeV and Γ _G ^{M 1} = 4.7±2.6 MeV. The neutron capture cross section of¹¹³Cd from its isomeric state ({ie147-02}=11/2^?, E ₁ ^m =263.7 keV) was calculated.     

Winkelkorrelationsmessungen an >30y Holmium 166 und Bestimmung desg R -Faktors des 4+-Rotationsniveaus von Erbium 166

The spins of several excited states of Er¹⁶⁶ have been investigated byγγ-angular correlation measurements. The spin sequence 0+, 2+, 4+, 6+ for the ground state rotational band was presumed to be correct. Unique assignments were derived for the states of 1076 keV, 1377 keV and 1785 keV asI=5, 7 and 6 respectively. These results are in agreement with the spins proposed byGallagher jr. andSoloviev. The multipolarities of theγ-transitions of 408 keV, 709 keV, 811 keV and 831 keV were derived as 95%E1+(5±1)%M2, 99·6%E1+(0·4±0·5)%M2, 99·1%E2+(0·9±0·3)%M1, and 96·1%E2+(3·9±1)%M1 respectively. The unusual mixing ratios of the transitions of 811 keV and 831 keV can be understood as a consequence of theK-selection rule. Eachγ-transition from the 1785 keV state should be stronglyK-forbidden and one expects a half-life ofT _1/2≈3·10^?9s. A measurement of the time spectrum of the coincidences between theβ-radiation and the high energyγ-lines gave however:T _1/2(1785 keV state)≦3·10^?10s. The rotation of the angular correlation between the 184 keV line and theγ-group at 820 keV has been measured in an external magnetic field of 53000 gauss as:ω·τ(4+)=0·083±0·006. This value contains small corrections for an additional rotation of the angular correlation of the 831 keV–184 keV triple cascade in the 6+state and for a small attenuation by internal fields. WithT _1/2(4+state)=1·23·10^?10s, andβ=7·08 one gets for theg-factorg _R=+0·266±0·024 in good agreement with recent results for the 2+ state.     

Die Diffusionskoeffizienten und mittleren freien Weglängen der geladenen und neutralen Radon-Folgeprodukte in Luft

The knowledge of the diffusion coefficients of radioactive atoms and ions in air is very important in a number of investigations on and computations of the attachment of radon decay products to aerosol particles. In this work measurements of the diffusion coefficients of neutral and charged²¹²Pb atoms are reported. The values found areD ₀=(7.6±0.4)·10^?2cm²s^?1 for neutral atomsD=(5.0±0.3)·10^?2cm²s^?1 for charged atoms The used method of measurement allowed to determine these constants 1–5 seconds after the formation aged²¹²Pb atoms, so that a “cluster” formation was improbable. The mean free path for neutral (λ₀=(4.9±0.3)·10^?6cm) and charged (λ=(3.2±0.2)· 10^?6cm) lead 212 atoms in air were computed from the measured diffusion coefficients. All obtained results were compared with values, calculated from theory.     

Molecular orientation correlations and reorientational motions in liquids carbon monoxide,nitrogen and oxygen at 77 K; A Raman and Rayleigh light-scattering study

Reorientational autocorrelation functions have been determined from measurements of depolarized vibrational Raman scattering for liquid carbon monoxide, nitrogen and oxygen at 77 K and atmospheric pressure. The autocorrelation functions, which for these liquids are not significantly affected by vibration-rotation interaction, reveal that free rotation is an important feature of the molecular motion in liquid nitrogen but is less important for carbon monoxide and oxygen. The differences in behaviour are discussed in terms of intermolecular forces.

New values for the depolarized Rayleigh scattering cross section have been determined from intensity measurements made relative to the 992 cm^-1 Raman line of benzene. These values are compared to those reported previously by the authors using a different intensity standard (Chem. Phys. Lett., 31, 355 (1975)). The scattering cross sections yield the following values , where ?_ij is the angle between the major axes of molecules i and j (i≠j) and P ₂ indicates the second Legendre polynomial: -0·15 ± 0·2 for CO, +0·30 ± 0·2 for N₂ and +0·40 ± 0·2 for O₂. The large errors result from uncertainties in the local field correction factor. The negative value for CO can be explained as a result of strong quadrupole interactions which tend to align neighbouring molecules perpendicular to one another. The forms of the reorientational cross-correlation functions determined from the current Raman data and previous Rayleigh data are briefly discussed.     

Activation measurement of the3He(4He,γ)7Be reaction

The energy integrated absolute cross section of the³He(⁴He,γ)⁷Be reaction has been determined by an activation measurement, using the branching of the⁷Be 53.44d β-decay to the 478 keV state in⁷Li and its subsequentγ-decay. Depending on the branching ratio used (10.4% or 15.4%) we obtain a zero-energy nuclear cross section factor ofS(0)=0.56±0.03 keV·barn orS(0)=0.38±0.03 keV·barn, respectively.     

Interference of Electromagnetic and Weak Interactions at High Energies and Neutral-Current μe Universality

A review is given on three types of experiments which recently detected the interference of electromagnetic and weak interactions at high energies in the reactions eD₂ → eX (SLAC, 1979), e⁺e⁻ → μ⁺μ⁻ (PETRA/PEP, 1981–83) and μ±C→μ±X (BCDMS, 1982). Asymmetry formulae are explicitely derived using the quark-parton model and the SU(2) × U(1) standard theory. With particular emphasis on the deep inelastic muon scattering experiment, the corresponding experiments are described and their results summarized. Combined fits to the 1983 asymmetry and νe data verify completely the muon-electron universality of the weak neutral current interaction giving for the vector and axial-vector coupling constants v_e = 0.02 ± 0.06, a_e = −0.54 ± 0.03 (electrons) and v_μ = −0.05 ± 0.16, a_μ = −0.51 ± 0.05 (muons).     

An N.M.R. study of molecular motion in solid trimethylaminegallane

Continuous wave and pulsed ¹H N.M.R. data have been obtained for solid H₃GaN(CH₃)₃ over the temperature range 63–300 K. A theoretical expression for the relaxation behaviour of a methyl group in a trimethylamine moeity undergoing various motions has been obtained to aid analysis of the data. We find the activation energy to rotation of the -GaH₃ group to be 3·6 ± 0·3 kJ/mole (0·86 ± 0·07 kcal/mole), and to a different motion in the molecule to be 21 ± 2 kJ/mole (5·0 ± 0·5 kcal/mole). In the continuous wave spectra effects due to motion of the -CH₃ groups and the whole -NMe₃ moeity may be distinguished.     

Effects ofpH on the chromophore orientation in purple membrane

Summary Suspensions of purple-membrane fragments from Halobacterium halobium were oriented by a static electric field with intensity up to 25V/cm in the range ofpH from 4 to 9. It was found that the orientation of the transient dipole moment of the retinal chromophore for what concerns the permanent dipole moment of the membrane fragment undergoes a transition from (60±1)° atpH 5 to (71±1)° atpH 6. Moreover, the permanent dipole moment of the membrane fragments of 1.8·10⁻²³ C·m found at thepH values from 4 to 7 reduces to 1.3·10⁻²³ C·m atpH higher than 7.

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Riassunto Sospensioni di frammenti di membrana purpurea del Halobacterium halobium apH fra 4 e 9 furono orientati da un campo elettrico statico d’intensità fino a 25 V/cm. Fu trovato che l’orientazione del momento di transizione di dipolo del cromoforo, il retinale, rispetto al momento di dipolo permanente dei frammenti di membrana subisce una variazione da (60±1)°apH 5 a (71±1)° apH 6. Inoltre, il momento di dipolo permanente dei frammenti di membrana di 1.8·10⁻²³C·m trovato nell’intervallo dipH da 4 a 7 si riduce a 1.3·10⁻²³C·m per valori dipH delle sospensioni maggiori di 7.