π-He interactions at T=106 MeV

interactions at have been studied by means of a self-shunted streamer chamber filled with helium at atmospheric pressure. This technique allowed reconstruction of the complete kinematics of the nuclear events under analysis, since tracks of slow p, α, tritium and ³He are readily measurable. The study revealed that the ⁴He nucleus behaves as a Planck radiator, emitting a Planck-like spectrum of high energy γs, when hit by a π beam of . A resonant behaviour in the π⁻n invariant mass spectrum has been observed, with and in the neutron knockout reaction: we consider this to be the first experimental evidence for the existence of the Δ⁻. The observed mass shift and width narrowing are compatible with the activation of an isobaric collective resonance in the ⁴He nucleus. The collaboration has also observed a resonant behaviour in the π⁻pp invariant mass spectrum in the pp double-charge-exchange reaction, on nuclear photoemulsion, compatible with the activation of the J^P=0⁻d^′ dibaryonic resonance with a strong p-p final state interaction. A new direct measured upper limit for the ν_μ mass has been derived by measuring a complete decay π-μ-e event recorded at the CERN PS179 experiment (Ne scattering): at a 90% confidence level, .     

Some results for a fractional diffusion equation with radial symmetry in a confined region

We investigate an N-dimensional fractional diffusion equation with radial symmetry by taking a spatial and time dependent diffusion coefficient into account, i.e.,  with . The equation is considered in a confined region and subjected to time dependent boundary conditions which may be related to inhomogeneous characteristics of the surfaces confining the system. The results show an anomalous spreading of the solutions and an unusual behavior of the survival probability.     

A simple mathematical model for anomalous diffusion via Fisher's information theory

Starting with the relative entropy based on a previously proposed entropy function , we find the corresponding Fisher's information measure. After function redefinition we then maximize the Fisher information measure with respect to the new function and obtain a differential operator that reduces to a space coordinate second derivative in the q→1 limit. We then propose a simple differential equation for anomalous diffusion and show that its solutions are a generalization of the functions in the Barenblatt-Pattle solution. We find that the mean squared displacement, up to a q-dependent constant, has a time dependence according to 〈x²〉∼K1/qt1/q, where the parameter q takes values (superdiffusion) and (subdiffusion), ∀n?1.     

Theory of antiferromagnetic exchange interaction for mixed-valent FeFe spin cluster in model complex of semimethemerythrin

The antiferromagnetic phenomena of both mixed valent Fe^IIIFe^II spin clusters and homodinuclear Fe^IIIFe^III clusters in complexes have been studied by means of our covalent magnetic exchange theoretical method. The sensitive relations between the exchange parameter J and the covalent factors N_A (for Fe^III) and N_B (for Fe^II) and the Fe?Fe separation R have been derived by use of our double-Slater function calculation procedure, the corresponding theoretical curve of J vs. N_A,N_B and R has been obtained. By taking the typical covalent factors of Fe^III and Fe^II, and using the observed Fe-O bond lengths: for Fe^III-O-Fe^II cluster in model complex {[Fe(acacen)]₂ONa}₂; for Fe^III-O-Fe^III cluster in oxyhemerythrin, we obtained the theoretical values: for Fe^III-O-Fe^II cluster and for Fe^III-O-Fe^III cluster. These are in good agreement with the corresponding experimental findings in {[Fe(acacen)]₂ONa}₂ and in oxyhemerythrin, respectively.     

Effect of exchange-coupling interaction on anisotropy of grain in nanoscaled magnets

The effect of inter-grain exchange-coupling interaction on the anisotropy of grain in nanoscaled magnets has been investigated by putting forward an expression of anisotropy at grain boundary, , which is suitable for different coupling conditions, and expresses well the coherency between soft and hard grains. The average anisotropy of grain 〈K^ij〉 has been calculated based on and the theory of partial exchange-coupling interaction. It has been found that the average anisotropy of hard or soft grain, 〈K^hh〉 or 〈K^ss〉, increases with increasing grain size D monotonously when hard-hard or soft-soft grains couple. When soft-hard grains touch each other, with increasing D, the variation of average anisotropy of soft-hard grain 〈K〉 depends on the anisotropy at grain interface , which denotes the affection degree of hard grain on the anisotropy of soft grain. Compared with other results, it is more reasonable that ranges from to . The variations of anisotropy with D we calculated are consistent with those of coercivities given by other authors when is fixed in a certain range.     

Laser induced fluorescence spectroscopy of NdO

Laser induced fluorescence spectra of ¹⁴²NdO have been excited using both fixed frequency argon ion and tunable ring dye lasers and detected at high resolution with a Fourier transform spectrometer. Nine low lying electronic states resulting from the Nd²⁺(4f³6s)O²⁻ configuration were detected of which four, the second lowest , 3, and 5 states, (2)2, (2)3, (2)5, and the lowest state, (1)6, have been observed for the first time. In addition, new vibrational levels were observed in the lowest , (1)5 (v=1) and second lowest , (2)4 (v=1, 2) states. Abnormally large Ω doubling in both states has been attributed to interactions involving neighboring and 0 states. Several perturbations were observed and used as an aid in assigning some of the states. Both the order and energies of the low lying states have been shown to be consistent with Ligand Field theory calculations. Rotational relaxation in several of the spectra has allowed calculation of accurate rotational constants for several states while, for other states, approximate parameters have been calculated from combination differences.     

The 2ν5 overtone bands of perchloryl fluoride

The high-resolution infrared spectra of the monoisotopic species F³⁵Cl¹⁶O₃, F³⁷Cl¹⁶O₃, F³⁵Cl¹⁸O₃ and F³⁷Cl¹⁸O₃ have been studied in the region of the 2ν₅ overtones, from 1100 to 1200 cm⁻¹. Both the parallel and the perpendicular components are clearly observed in the spectra, their origins differing by about 0.4 cm⁻¹. In each spectrum about 2000 transitions have been assigned, 35% of them belonging to . The parallel and perpendicular bands in each manifold have been analyzed separately since no evidence of perturbations has been observed. The rovibration parameters of the v₅ = 2, l₅ = 0 and v₅ = 2, l₅=?2 excited states have been obtained. For the four species combining the and band origins with those of the ν₅ fundamentals the harmonic wavenumbers, , and the x₅₅ and g₅₅ anharmonicity constants have also been derived.     

Maximising rovibrational assignments in the ν1 band of NSCl by spectral analysis by subtraction of simulated intensities (SASSI)

The ν₁ band of thiazyl chloride (NSCl) has been measured by high resolution FTIR spectroscopy, and studied using the spectral analysis by subtraction of simulated intensities (SASSI)-technique. This involves assignment and fitting of a component, creating a global simulation of the entire component to be subtracted from the experimental spectrum, and subsequent analysis of the resultant spectrum. Through this iterative procedure it has been possible to assign rovibrational transitions for seven components, with populations in the lower vibrational state as low as 2% of the total. The components are the fundamental and , , and hotbands of ¹⁴N³²S³⁵Cl, the fundamental and hotband of ¹⁴N³²S³⁷Cl, and the fundamental of ¹⁴N³⁴S³⁵Cl. Rotational and centrifugal distortion constants beyond the quartic level have been obtained by fitting to Watson’s A-reduced Hamiltonian in upper and lower states.     

Sub-Doppler high-resolution excitation spectroscopy of the S1 ← S0 transition of dibenzofuran

Rotationally resolved ultrahigh-resolution fluorescence excitation spectra of the S₁ ← S₀ transition of dibenzofuran have been observed using the technique of crossing a collimated molecular beam and the single-mode UV laser beam. 3291 rotational lines of the band and 3047 rotational lines of the band have been assigned. The band has been found to be a b-type transition, in which the transition moment is along the twofold symmetry axis of this molecule, and only the ΔK_a = ± 1 transitions were observed. The excited state is identified to be the S₁¹A₁(ππ^∗) state. In contrast with this, the band has been found to be an a-type transition in which the transition moment is along the long axis in plane. It indicates that the intensity of this vibronic band arises from vibronic coupling with the S₂¹B₂(ππ^∗) state. We determined the accurate rotational constants and the molecule have been shown to be planar both in the ground and excited states.     

Measurement of ultraweak transitions in the visible region of molecular oxygen

A highly sensitive cavity-enhanced frequency modulation spectroscopy technique has been used to measure ultraweak transitions in molecular oxygen that had not previously been characterized. The self-broadened half-width and line intensity of the measured transitions are reported. We include 12 high J transitions in the band of ¹⁶O₂ (the so-called A band), 59 transitions in the hot band of ¹⁶O₂, and 17 high J transitions in the band of ¹⁶O¹⁸O. Our measurements of line positions of the ¹⁶O¹⁸O transitions are used to determine improved molecular constants for the excited state of ¹⁶O¹⁸O.     

Laser spectroscopy of the A9-X8 transition of holmium monochloride

Using laser excitation spectroscopy, 18 red-degraded bands belonging to a single electronic transition of holmium monochloride have been observed in the 615-670 nm region. Thirteen of the bands, with vibrational levels 0?v^′?3 and 0?v″?4 have been obtained at high resolution and rotationally analyzed. Observation of the first lines in some of the bands has shown that Ω=8 in the ground state and Ω=9 in the upper state. By analogy with HoF, this transition has been labeled as A9-X8. The Ω=8 assignment for the X state establishes the ground state configuration of HoCl as Ho⁺(4f¹⁰6s²)Cl⁻, in accord with predictions of Ligand Field Theory. From the rotational analysis, the main equilibrium molecular constants of , for the upper state and , for the ground state have been obtained.     

Vibration-internal rotation-overall rotation interactions in CH3OH. II. Vibration introduced τ-dependence to the reduced kinetic energy coefficient for internal rotation

Vibration-internal rotation-rotation interaction theory has been used to calculate the τ-dependence of F, the reduced kinetic energy coefficient for internal rotation for CH₃OH from molecular structure. The leading term is as a fraction of F⁰. Smaller terms are and then and for the symmetry breaking terms of the vibrationally distorted molecule. These terms have not been included previously in torsion-rotation anaylses for CH₃OH but should be compared with the fractional uncertainty in F⁰ of ±7×10⁻⁷. A rough estimate of the τ-independent vibrational contributions to F⁰ is of the order 4% with the largest contributors being the COH bend and OH stretch.     

EPR study of Mn-implanted single crystal plates of TiO2 rutile

Single crystals of Mn-implanted TiO₂ rutile have been investigated by electron paramagnetic resonance (EPR) technique at room temperature. We have observed an EPR signal on Mn⁴⁺ ions (S=) in the manganese-implanted single crystal TiO₂ plates. Besides, weaker EPR signals due to Fe³⁺(S=, L=0) and Cr³⁺(S=) ions have also been observed. Characteristic six-line splitting of the manganese EPR lines due to hyper-fine interaction with ⁵⁵Mn nuclei (spin I=) has also been observed. Analysis of the EPR spectra shows that the manganese, iron and chromium ions substitute for Ti⁴⁺ ions in the TiO₂ rutile host. Two structurally equivalent groups of the centers have been observed in the EPR spectra in correspondence with two octahedral positions of the Ti ions in the rutile structure. Spin Hamiltonian parameters for the crystal field of orthorhombic symmetry on the Mn⁴⁺, Fe³⁺ and Cr³⁺ centers have been obtained as result of computer modelling.     

The 2ν4 overtone bands of FClO3

The high resolution infrared spectrum of the mono-isotopic species F³⁵Cl¹⁶O₃ has been studied in the region of the 2ν₄ overtone, from 2560 to 2680 cm⁻¹. The perpendicular component is strong and clearly observed while the parallel component is very weak and almost completely hidden by the perpendicular one. Their origins differ by 12.6 cm⁻¹, the being located at higher wavenumbers. The band is perturbed by the anharmonic interaction between the v₄ = 2, l₄ = ?2 and v₂ = v₄ = v₅ = 1, l₄ = l₅ = ±1 excited states, both of E symmetry. In total 3157 transitions have been assigned, 83% of these to , 12% to , and 5% to . The three bands have been analyzed simultaneously, taking into account the Fermi resonance effective between the excited states of E symmetry. The ro-vibration parameters of the excited states have been obtained, including the deperturbed band origins of and , at 2628.5890(4) and 2619.3342(5) cm⁻¹, respectively. The W₂₄₅ anharmonic constant is equal to 4.0161(4) cm⁻¹. The x₄₄+g₄₄ and x₂₄+x₄₅+g₄₅ anharmonicity constants have been derived from the obtained band origins and those of ν₄ and ν₂ + ν₅.     

Characterization of Tm doped mixed alkali borate glasses—spectroscopic investigations

The effect of mixed alkalis on the optical absorption spectra of Tm³⁺ in xNa₂O·(30−x)K₂O·70B₂O₃ glasses has been studied. The optical band gap values (E_opt) for both direct and indirect transitions have been obtained using Davis and Mott theory. Spectroscopic parameters like Racah (E¹, E² and E³), spin-orbit (ξ_4f) and Judd-Ofelt intensity parameters (, and ) have been calculated for different x values. Radiative transition probabilities (A_rad), radiative lifetimes (τ_R), branching ratios (β), integrated absorption cross sections (Σ) and multiphonon relaxation rates (W_MPR) are calculated for certain excited states of Tm³⁺ ion. The observed trends in the above parameters as a function of x in these borate glasses have been discussed keeping in view the effect of mixed alkalies in borate glasses. Certain potential lasing transitions have been identified for laser action among the various transitions of Tm³⁺ in these mixed alkali borate glasses.