First experimental observation of the conical effect in Smith–Purcell radiation

The conical effect in Smith–Purcell radiation arising from electrons moving at non-zero angle to the direction of grating periodicity has been observed for the first time. It was found that the maximum of radiation intensity for ψ ≠ 0 shifts in both polar and azimuth angles. The experimental and theoretical results were compared, and the good agreement was shown. The experiment has been performed for 6 MeV electrons and at millimeter wavelengths.     

First observation of γγ → ωω

The reaction γγ → 2π⁺ 2π⁻ 2π⁰ has been studied using the ARGUS detector at the e⁺e⁻ storage ring DORIS II at DESY. Production of ω mesons is observed and, in particular, the reaction γγ → ωω is seen for the first time. The cross section for γγ → ωω has an enhancement at ∼ 1.9 GeV/c² of about 10 nb. The cross sections for γγ → 2π⁺ 2π⁻ 2π⁰ and γγ → ωπ⁺ π⁻ π⁰ are also given.     

First observation of the KS→π0γγ decay

Using the NA48 detector at the CERN SPS, 31 K_S→π⁰γγ candidates with an estimated background of 13.7±3.2 events have been observed. This first observation leads to a branching ratio of BR(K_S→π⁰γγ)_z>0.2=(4.9±1.6_stat±0.9_syst)×10⁻⁸ in agreement with Chiral Perturbation Theory predictions.     

Pressure broadening of methane lines in the 6190Åand 6825Åbands at room and low temperatures

Measurements of pressure broadened half-widths have been performed for one vibration-rotation line in the 6190Åmethane band and one vibration-rotation line in the 6825Åmethane band. Self-, nitrogen-, hydrogen- and helium-broadening have been measured over a temperature range of 77–295 K. Pressure broadening coefficients and temperature dependence indices have been obtained for each line and broadening gas.     

First observation of the decay φ→η′(958)γ

The decay φ→η′γ has been observed by the CMD-2 detector at the e⁺e⁻ collider VEPP-2M at Novosibirsk. Of 5.5 million produced φ's, six events of the φ→η′γ decay were selected with the expected background less than one event. The corresponding branching ratio is B(φ→η′γ)=1.2^+0.7_−0.5·10⁻⁴. It is the first observation of this radiative decay.     

First observation of the ν9/2[404] orbital in the A ∼ 100 mass region

A new band, populated by the spontaneous fission of ²⁴⁸Cm and studied by means of prompt γ-ray spectroscopy using the EUROGAM2 array, was observed in ⁹⁹Zr. The 1038.8 keV band head with a half-life T _1/2 = 54(10) ns is interpreted as a K-isomer, corresponding to the 9/2[404] neutron-hole excitation. It is the first observation of this orbital in the mass A ∼ 100 region. The quadrupole moment, Q ₀ = 3.9(3) eb deduced for the new band indicates a large deformation of β = 0.41, which is produced by a specific shape-coexistence mechanism, known in other regions and now found in the A ∼ 100 nuclei. Received: 11 September 2002 / Accepted: 31 October 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: urban@fuw.edu.pl Communicated by D. Schwalm     

STM of isolated complexes of R-Phycoerythrin: direct observation of the γ-subunit at the centre of the complex

Scanning tunnelling microscopy was used to study the topography of single complexes of the photosynthetic protein R-Phycoerythrin and to determine the location of the γ-subunit. This study has resolved an ambiguity in the positioning of the γ-subunit from X-ray crystal structure analysis which arose from the symmetry-related averaging of the X-ray diffraction pattern which led to a loss of resolution.     

Possibility of the odderon discovery via observation of charge asymmetry in the diffractive π+π− production at HERA

It is shown that the energy deposition pattern in deep calorimeters could be the spectacular and unconventional signature of different kinds of stable and unstable strangelets. As an example the detection method of strongly penetrating objects, such as strangelets possibly produced in the baryon-rich environment formed in central Pb-Pb collisions at LHC energies, is described.     

Proton-neutron interaction at N≅Z — First observation of the Tz=1 nucleus 46 94 Pd48 in-beam

The neutron deficient nucleus⁹⁴Pd was identified and studied for the first time by in-beam spectroscopy. An I=(14⁺) isomer with t_1/2=0.8 (2) s was observed in a recoil catcher setup inside the multi-detector -array OSIRIS. Filter detectors for neutrons and charged particles were used to identify the (2p2n) exit channel of the reaction⁵⁸Ni+⁴⁰Ca, populated with only 0.06% of the total evaporation residue cross section. The structure of the isomer is discussed within the frame work of shell model calculations in the (p_1/2,g_9/2) model space with emphasis on the g ₉ ^2/2 T=0, I=1,9 pairing two-body matrix elements.Communicated by: D. Schwalm     

Lasing at 139 Å in nickel-like silver plasmas

Today, one of the key applications for X-ray Lasers is ICF-relevant plasma density diagnostics through interferometry techniques. Due to the peak reflectivity of the involved Mo/Si multilayer optics, the CEA/DAM studies have been focused on collisionnally excited population inversions in Ni-like silver plasmas. In order to optimize their X-ray output at 139 Å, various configurations have been investigated. One of them has recently been demonstrated at the P102 facility and has allowed 10¹¹ photons per pulse to be delivered, i.e. 2 μJ in 7 ps.     

Prevalent Dynamics at the First Bifurcation of Hénon-like Families

We study the dynamics of strongly dissipative Hénon-like maps, around the first bifurcation parameter a* at which the uniform hyperbolicity is destroyed by the formation of tangencies inside the limit set. We prove that a* is a full Lebesgue density point of the set of parameters for which Lebesgue almost every initial point diverges to infinity under positive iteration. A key ingredient is that a* corresponds to the “non-recurrence of every critical point”, reminiscent of Misiurewicz parameters in one-dimensional dynamics. Adapting on the one hand Benedicks & Carleson’s parameter exclusion argument, we construct a set of “good parameters” having a* as a full density point. Adapting Benedicks & Viana’s volume control argument on the other, we analyze Lebesgue typical dynamics corresponding to these good parameters.     

Measurement of sensitivity of transducer in the field of NDT by the reciprocity technique

The sensitivity of a transducer should be an important characteristic inthe field of NDT.But so far,no method for this measurement of the sensitivity of atransducer applied to the ultrasonic flaw detection is available.In this paper thetransducer is regarded as a plane source and the reciprocity parameter under thecondition of the far field is derived.We have calibrated the sensitivity of ultrasonictransducers with the reciprocity technique in the solid sample.The experimentsshow and confirm that the transmitting and receiving sensitivities of the transducerapplied to NDT can be exactly measured.The precision of the measurement is with-in ± 1dB under a certain coupling condition.     

Further observations on the polarized absorption spectrum of benzene crystals at 2000 Å

The structure of a hard sphere fluid confined by model slit and cylindrical pores is investigated. Results from grand canonical Monte Carlo (GCMC) simulations and from the hypernetted chain/mean spherical approximation (HNC/MSA) equation are reported. GCMC results are compared with those from the HNC/MSA equation, and agreement is good. The effect of confinement on liquids at the same chemical potentials is that the absorption of the hard sphere fluid into the pores decreases with increasing confinement, i.e., when going from planar to cylindrical geometry or by narrowing the pores. The adsorption on the pore walls has, in general, the opposite behaviour. For high bulk concentrations and certain values of cylindrical pore diameter the concentration profile is higher at the centre of the pore than next to the pore wall. A very strong, but continuous, transition occurs in the concentration profile, as a function of the cylinder's diameter. These results could be of some interest in catalysis studies.     

Theoretical study of thermal diffusivity of superlattices in measurements using “mirage” technique

A complete theoretical treatment for the determination of thermal diffusivity of superlattices by the mirage technique has been performed. An effective medium approximation model of the thermal conductivity and thermal diffusivity of both sublayers is presented, which is different from the simple models with the thermal diffusivity or thermal conductivity in series or parallel. The numerical calculation of the transverse component of the probe beam deflection in the mirage effect shows that the results obtained from the complete thermal-wave theory and the medium approximation model, for the optically and thermally thick superlattices, are in good agreement with each other. However, the further study on the thermally thin superlattices shows that either the series or the parallel model of the thermal conductivity should be chosen according to whether the thermal impedance of the superlattice is larger or less than that of substrate, respectively.     

Optogalvanic spectra of calcium in the 6090–6760 Å region

Optogalvanic spectra of some 30 transitions of calcium originating from the ground state as well as from several excited states (4s4p ^1,3P, 4s3d ^1,3D, 4s5p ³P, 3d4p ³D, ³F) have been investigated using laser-irradiation of a low-current glow discharge in a thermionic diode. The influence of various experimental parameters such as bias field, oven temperature and buffer gas pressure on the spectra are reported. Seven previously unreported transitions are recorded including four forbidden transitions which violate the J selection rules. An interesting anomaly observed in the non-statistical population of the 4s3d ³D_3,2,1 multiplet is discussed where the populations of ³D₃:³D₂:³D₁ are in the ratio of 94:5:1. A possible explanation is based on avoided crossing between potential energy curves of the Ca-Ar molecule.