Parametrization of the S0 two nucleon transition matrix

The ¹S₀ two-nucleon transition matrix T is constructed from the symmetric part σ of its half-shell elements. The on-shell component of σ is given by the phase shift, while a wide class of parametrizations is suggested for the off-shell part. Restrictions on the off-shell part of σ arising from the short range and the proper one-pion-exchange tail of the nucleon-nucleon interaction are investigated. Using σ in the ¹S₀ and the Reid soft-core potential in the other partial waves, the binding energy per particle in nuclear matter and ¹⁶O and the ¹⁸O shell-model spectrum are computed. The sensitivity of these nuclear-structure results is tested with respect to (i) smooth off-shell changes in σ, (ii) various assumptions on the high-energy phase shift, (iii) the charge dependence of the phase shift, and (iv) experimental uncertainties in the phase shift.     

Three-nucleon calculations without the explicit use of two-body potentials

Using as two-nucleon interaction input the ³S₁-³D₁ and ¹S₀ partial waves, the Faddeev equations are solved for the three-nucleon bound state. The ³S₁³D₁T-matrix is calculated from the Reid potential. Avoiding the usual potential fit, the ¹S₀T-matrix is directly continued off-shell and is constructed consistent with the ¹S₀ phase shift of elastic two-nucleon scattering. The off-shell part of the ¹S₀T-matrix is parametrized and with this parametrization the dependence of the three-nucleon bound-state properties is studied. As a result it is found that the binding energy varies only between 6.2 MeV and 6.8 MeV, while the minimum in the charge form factor for electron scattering from ³He lies between 12.9 fm^?2 and 18.7 fm^?2. The larger (smaller) ³He binding energy is accompanied by a ³He charge form factor whose minimum is at larger (smaller) momentum transfers.     

Local potentials phase equivalent to separable two-nucleon interactions

Local energy-dependent potentials have been constructed phase equivalent to members of a family of phase-equivalent separable two-nucleon potentials in the¹ S ₀-state. It has been shown that these potentials obey the known off-shell constraints in the¹ S ₀-state and can therefore not be regarded as unrealistic in this sense. They have the same shape as the energy-independent local Kermode potentials. However we also find that the off-shell behaviour of a separable¹ S ₀ potential and its local equivalent can differ considerably.     

A constraint on the off-shell effective range parameter in p-p scattering

Sauer has recently proposed fixing the zero-energy ¹S₀ state wave function as a means of constraining the off-shell behaviour of the N-N interaction. We propose as an alternative that the value of the off-shell effective range parameter I₀ be constrained. A value of I₀ = 13 ± 1 fm³ seems to be indicated if charge symmetry is required.     

The boundary condition approach to nucleon-nucleon potentials and the calculation of the T- and K-matrices

It has been shown that the off-shell T- and K-matrices can be obtained by means of boundary conditions imposed upon the off-shell wave function only. When there is a potential outside the boundary condition radius the method proposed permits to deduce in a rather simple way a renormalized Lippmann-Schwinger equation. The S-components of the T- and K-matrices are considered in detail using a potential of the exponential type in the exterior region. For such types of potentials a rather effective method for factorizing the K-matrix is given. Parameter fits to the ¹S₀ and ³S₁ phases are presented.     

Phenomenological separable potential of K + N interaction for J≤15/2

A nonlocal separable potential of K ⁺ N interaction in the isospin-0 and isospin-1 S, P, D, ..., J scattering channels is constructed. This potential describes satisfactorily the results of the SP92 phase-shift analysis (R. Arndt) at incident-kaon energies in the interval from 0 to 2.4 GeV. The off-shell amplitudes for kaon-nucleon scattering are calculated. They are shown to differ significantly from the commonly used off-shell amplitudes.     

Method for Lippmann-Schwinger equations

A recently proposed degenerate-kernel scheme for solving Fredholm integral equations of the second kind is extended to singular equations of the Lippmann-Schwinger type. Numerical calculations of on- and off-shell t-matrix elements are carried out at positive and negative energies, for the ¹S₀ Reid soft-core nucleon-nucleon potential. Satisfactory convergence is achieved, even with the simplest version of the s     

The equilibrium structure of disulfur monoxide: Diode laser spectroscopy of ν1 and ν3 of S218O and ν3 of S216O

Diode laser spectroscopy of ν₁ and ν₃ of ³²S₂¹⁸O and ν₃ of ³²S₂¹⁶O has been carried out and several hundred transition frequencies were measured with a nominal accuracy of ±0.001 cm⁻¹. These data have been combined with earlier microwave and diode laser measurements to produce accurate rotational and distortion constants for the (0, 0, 0), (1, 0, 0), and (0, 0, 1) vibrational states of both isotopic species. These results were combined with microwave data from (0, 1, 0) of both isotopes to allow and equilibrium structure for S₂O to be calculated.     

Anomalous electrical conductivity of the potassium deficient linear chain platinum compound: K1.75Pt(CN)4·1.5H2O

Four probe single crystal dc conductivity, σ, has been measured for K_1.75Pt (CN)₄·1.5H₂O for temperature 360K > T > 30K on crystals prepared via electrochemical growth, with σ (295K)

25–50 Ω^?1cm^?1. An anomalous behavior in σ (T) is reported with σ (T) nearly constant for T > 300K and 160K > T > 80K, and rapidly decreasing σ (T) observed for 300K > T > 160K and T < 80K. The data for 200K < T < 308K are analyzed in terms of a three-dimensional second order phase transition occurring at T_c = 308K. These results contrast sharply with those of the well studied K₂Pt(CN)₄X_0.3·3H₂0 (X=Cl,Br).     

S0 and S1 spectroscopy of jet cooled 9-cyano-10-methylanthracene: The methyl group as a molecular rotor

Jet-cooled fluorescence excitation and dispersed fluorescence spectra of 9-methylanthracene (MA), 9-cyanoanthracene (CA) and 9-cyano-10-methylanthracene (CMA) have been measured. The spectra of MA and CMA near the S₀-S₁ origin reveal a prominent torsional progression due to the hindered methyl group rotation and its torsional vibration against the aromatic ring frame. Additionally, the laser induced fluorescence LIF excitation spectrum of CMA shows the splitting of many vibrational modes.Observed positions and relative intensities of the methyl internal rotational bands were interpreted in terms of transitions calculated based on the quantum mechanical one-dimensional rotor. The low-frequency vibrational bands were interpreted also with the all electron quantum mechanical calculations within the RHF/6-31G(d,p), CIS/3-21G and CIS/6-31G(d,p) approximations. It is predicted that in the case of MA the eclipsed geometry (one C-H in the plane of the ring) is most stable in both S₀ and S₁ states. Conformation of the methyl group in CMA is suggested to change upon S₁ ← S₀ excitation (π/12 phase shift of the methyl group). The predicted energy barrier for methyl group rotation in the S₀ state of CMA is considerably higher (72 cm⁻¹) than that in the S₁ state (22 cm⁻¹). Following the present quantum mechanical calculations, the carbon atom of the methyl group belongs to the aromatic plane in the S₀ ground state but it deviates from this plane in the S₁ excited state. These in turn suggest that the calculated barrier for methyl group rotation in CMA has a 6-fold symmetry in the S₀ ground state and roughly a 4-fold symmetry in the S₁ state.     

Low-frequency noise in monodisperse platinum nanostructures near the percolation threshold

The percolation threshold p ₀ ≈ 0.6 is determined for monodisperse platinum nanostructures with 1.8-nm metallic particles deposited in a monolayer onto an insulating substrate through laser electrodispersion. It is shown that, in the “metallic” state (for p > p ₀), both the magnitude of the noise and its temperature dependence are close to those of pure metallic Pt layers. The frequency dependence of the normalized noise power spectral density is described by the relationship S _I /I ² ～ 1/f ^γ with the exponent γ close to unity. For current densities j ≥ 10⁷?10⁸ A/cm², the noise power spectral density S _I increases more rapidly with a further increase in the current as compared to I ² because of the current generating excess defects. For p < p ₀, the dependence of the conductivity σ on the temperature is adequately described by the standard relationship σ ～ exp[?(T ₀/T)^1/2]. The normalized noise power spectral density S _I /I ² exceeds the corresponding value for a quasi-metallic structure by many orders of magnitude. The noise power spectral density S _I is approximately proportional to the square of the current only for very low currents and increases steeply with a further increase in the current.     

The deuteron wave function at short range and the triton

It is shown that if one assumes something between zero and the prediction of the scaling model with dipole fit for the neutron electric form factor, then a variety of short-range behaviour for the deuteron wave function is consistent with existing experimental data on the deuteron electric form factor. This still relatively wide latitude for the inner deuteron wave function, consistent with existing experimental electromagnetic data, gives rise to an off-shell variation of approximately 1.2 MeV in the triton binding energy with a fixed ¹S₀ interaction and a P_D varying from 4.5 to 6.5 %. Interactions with greater densities of matter at short range bind the triton more strongly and closer to the experimental value. An off-shell variation of 0.7 MeV is obtained with a fixed p_d and singlet interaction. However, a single measurement of the deuteron tensor polarization at about q² = 20 fm^?2 would severely restrict this variation.     

The rs structure of disulfur monoxide: The microwave spectrum of S218O

In a novel flow system 95 at.% enriched S₂¹⁸O was produced and the microwave spectrum in the states (0, 0, 0) and (0, 1, 0) was observed. The resulting constants together with the data already published allowed the complete r_s structure of S₂O to be determined.     

A separable potential model for S0 neutron-proton interaction

A two-term separable potential is proposed for the ¹S₀ neutron-proton interaction. This potential is very soft. Its off-shell behaviour is very similar to that of a local potential.     

Measurement of the quadratic Zeeman shift of Rb hyperfine sublevels using stimulated Raman transitions

We demonstrate a technique for directly measuring the quadratic Zeeman shift using stimulated Raman transitions. The quadratic Zeeman shift has been measured yielding Δν=1296.8±3.3 Hz/G² for magnetically insensitive sublevels (5S_1/2,F=2,m_F=0→5S_1/2,F=3,m_F=0) of ⁸⁵Rb by compensating the magnetic field and cancelling the ac Stark shift. We also measured the cancellation ratio of the differential ac Stark shift due to the imbalanced Raman beams by using two pairs of Raman beams (σ⁺, σ⁺) and it is 1:3.67 when the one-photon detuning is 1.5 GHz in the experiment.     

Model dependence of the Coulomb-corrected p-p scattering length

It is shown that the requirement of a fixed intermediate-range ¹S₀ proton-proton interaction considerably reduces the model dependence of the Coulomb-corrected p-p scattering length. A possible relation with the off-shell effective range parameter is discussed.     

Meson pair production in γγ scattering and implications for scalar mesons

We describe a simple analytic unitary model which provides with a parametrization of low energy (from threshold up to 1.4GeV) two photon production of ππ andK \(\bar K\) pairs in term of a few parameters related to the γγ width of the scalar and tensor resonances. It can be useful for analysing data because of the large continuum found in γγπ⁺π^? production besides thef ₀ (1,270) peak in recent experiments. We show that the present data already provides a strong evidence for the existence of a broad low mass scalar state, the old σ or ε (600) with a γγ width of 5 to 9KeV, and that it will be difficult to get more information on the controversialS ^* parameters from ππ pair production only. In thef ₀ range we explain the downwards shift of the π⁺π^? peak but we expect the π⁰π⁰ peak around 1.27–1.29 GeV which could raise the question either of systematic errors in mass calibration of crystal Ball experiment or of the precise value of thef ₀ mass.     

Interactions between SO2 and NO on the surface of stepped Pt(3 3 2)

Interactions between S¹⁸O₂ and NO on the surface of stepped Pt(3 3 2) were studied using Fourier transform infra red reflection-absorption spectroscopy (FTIR-RAS) combined with thermal desorption spectroscopy (TDS). Adsorbed S¹⁸O₂ does not seem to have a preference for step sites on Pt(3 3 2). As such, the presence of S¹⁸O₂ molecules following exposures of ?1.6 L does not significantly block the subsequent adsorption of NO (?0.8 L) on these step sites. Adsorbed S¹⁸O₂ molecules undergo dissociation (S¹⁸O₂(a) → S¹⁸O(a) + ¹⁸O(a)) as the surface temperature is increased to 250 K and above, but the resultant ¹⁸O(a) further reacts with sulfur oxides (S¹⁸O₂(a) and S¹⁸O(a)) to form S¹⁸O_x (x > 2) species at ∼400 K and above. The S¹⁸O_x species desorb as S¹⁸O₂. Even though the presence of co-adsorbed S¹⁸O₂ suppresses NO dissociation and subsequent N₂ production, this effect is not significantly enhanced with increasing the exposures of S¹⁸O₂ in the range ?1.6 L; N₂ desorption is still detectable at an exposure of 1.6 L S¹⁸O₂, at which a considerable amount of S¹⁸O₂ desorption is detected.     

Isotope dependence of the rotational constant of sulfur monoxide in the 3Σ-ground state

The rotational spectra of ³²S¹⁶O, ³⁴S¹⁶O and ³²S¹⁸O were measured. The rotational constant B₀ was accurately determined for all three isotopes whereas the spin-spin coupling λ₀ and the spin-rotation coupling γ₀ have less accuracy due to the strong correlation of these constants for the observed transitions. The evaluated breakdown of the Born-Oppenheimer approximation can primarily be attributed to the nonadiabatic correction term found for ¹Σ-diatomic molecules. The small adiabatic correction for SO is obtained with the opposite sign as usually derived in ¹Σ-molecules.