A. Filevich

Spectral-directional reflectivity of Tyvek immersed in water

Abstract Spectral-directional relative intensity of the light scattered by a Tyvek sample, immersed in water, has been measured for visible and UV wavelengths. The obtained information is useful to simulate the behavior of light in water Cherenkov detectors, such as those proposed for the observation of high energy cosmic ray air showers. In this work a simple empirical dependence of the scattering pattern on the angle was found, convenient to be used in Monte Carlo simulation programs.

Level structure of 72As studied with the (α, xnp) reaction

Abstract States of 72 As, excited through the 70 Ge(α, np) and 72 Ge(α, 3np) reactions at E α = 30 to 55 MeV, were studied. Excitation functions, γ-ray angular distributions, γ-γ coincidences and γ-time distributions with respect to the beam bursts, were determined. Five excited states are identified with levels previously observed with the (p, n) reaction. In addition seven new levels and their decay pattern are incorporated into a level scheme. A half-life of 17 ± 3 nsec was determined for the 309.8 keV state, and evidence for the existence of a long-lived state (>100 nsec) was obtained. A simple scheme based on simple particle shell-model configurations accounts for the gross properties of the low lying levels. While definite spin and parity assignment for the upper excited states require further measurements, tentative spin values up to 7 are obtained.

Examination of nuclear measurement conditions in cold fusion experiments

The recent announcement of electrochemically induced nuclear fusion [1,2] has generated great interest and activity within the scientific community. In particular, there are several aspects related to the work of ref. 1 which are not fully understood and therefore deserve further investigation. One of them is the huge discrepancy between the amount of measured heat and the intensity of the supposedly accompanying nuclear radiation, namely neutrons and gamma rays. In view of the fact that the detection of nuclear radiation in the context of an electrochemical process is perhaps the most unequivocal fingerprint for the occurrence of fusion, we feel that a careful re-evaluation of the measurement conditions may be needed. In order to address this question, in the present paper we report on an attempt to observe this phenomenon and on the possible problems related to the detection techniques.

A water tank Cherenkov detector for very high-energy astroparticles

Abstract Extensive airshower detection is an important issue in current astrophysics endeavours. Surface arrays detectors are a common practice since they are easy to handle and have a 100% duty cycle. In this work we present an experimental study of the parameters relevant to the design of a water Cherenkov detector for high-energy airshowers. This detector is conceived as part of the surface array of the Pierre Auger Project, which is expected to be sensitive to ultra high-energy cosmic rays. In this paper we focus our attention in the geometry of the tank and its inner liner material, discussing pulse shapes and charge collections.

Level structure of 76Br from the 75As(α,3nγ) reaction

Abstract Hitherto unknown states of 76Br were excited through the (α, 3nγ) reaction on 75As at Eα = 30 to 55 MeV. Excitation functions, γ-ray angular distributions, γ-γ coincidences and the γ-ray emission time with respect to the beam bursts were determined. Levels above the 1− ground state at energies (in keV) with the following spin-parity assignments are proposed: 141.8, 2; 253.7, 3−; 491.8, 4; 584.9, 5−; 1016.3, 6. These levels exhibit the energy spacings of a Coriolis-perturbed rotational band and the branching ratios show collective behavior. The comparison of these levels with those of the 5 2 + ground-state band recently reported in 77Kr show that (a) the Coriolis effects are quite similar and (b) the first two excited levels lie very close in energy in both cases. The possibility that these two facts indicate the validity of the rotation aligned coupling scheme in a doubly odd system is discussed.

Level structure of 73Se from the 72Ge(α, 3nγ) reaction

Abstract States of 73 Se, excited through 72 Ge(α, 3nγ) at E α = 30 to 55 MeV, were studied. Excitation function, γ-ray angular distributions and γ-γ coincidences were determined. Levels at the following energies in keV (spin-parity) are proposed: 151( 3 2 − ), 505( 5 2 − ), 804( 7 2 − ) and 1178( 9 2 − ). These levels, together with the hitherto known 1 2 − state at 25 keV, exhibit a K = 1 2 quasi-rotational structure as regards the energy spacings and branching ratios. A similar recent finding in 75 Se suggests that such a structure is not uncommon in this region of the periodic table. In spite of its spin, no decay into the 7 2 + ground state, interpreted by Kuriyama et al. as a deformed three dressed quasiparticle state, is observed although such a decay should be favoured in the present reaction.

High-spin states in 49Ti and the empirical (f72)n model

Abstract High-spin states in 49 Ti have been populated through the 48 Ca(α, 3n) reaction. Excitation function, γ-ray angular distributions, γ-γ coincidences and half-lives were determined. Levels with the following energies (in keV) spins and parities are proposed 1542.5, 11 2 − ; 2505.8, 15 2 − ; 3290.6, 17 2 − and 4382.6, 19 2 (−) . These levels and their decay scheme are found to be very well described by the empirical ( f 7 2 ) n model.

In-beam study of 70As

Abstract Nuclear states of 70 As were studied through the 69 Ga(α, 3n), 60 Ni(12C, np) and 63 Cu( 10 B, 2np) reactions at various bombarding energies between 30 and 55 MeV. Excitation functions, γ-ray angular distributions, γ-γ coincidences, and γ-time distributions with respect to the beam bursts, were determined. Levels at 32.0, 167.0, 390.4, 485.4, 566.7, 869.1, 887.9, 898.7, 933.4, 1045.7, 1675.9, 1752.0, 1809.2, and tentatively at 2030 keV, were observed. All levels below 900 keV can be identified with levels seen with the (p, nγ) reaction. Tentative spin assignments extend up to J = 9. Two previously reported isomers are confirmed. The present measurements yield 3.3±0.7 and 4.4±0.1 ns for the 485.4 and 887.9 keV states, respectively. No collective features, as in the lighter isotone 68 Ga, were found. The levels below 1 MeV are likely to be described by simple shell-model configurations. The spacing of the proposed J = (4), (5), and (6) levels is analogous to that in 72 As and 74 As. The behavior of their excitation energy as a function of N suggests the configurations {π p 3 2 −1 , ν g 9 2 } or {π f 5 2 , ν g 9 2 } for these states.

In-beam study of 78Br

Abstract High-spin states in 78Br decaying into the 4+ isomer at 180.8 keV were excited via the 77Se(α, 2np) and 76Ge (7Li, 5n) reactions. A sequence of closely lying levels with I ⩽ 8 is found between 227.6 and 467.6 keV. The highest state in this group is populated by a relatively strong 904.1 keV ΔI = 2 transition. These features provide a basis for a comparison with the positive-parity ground-state Coriolis-distorted band of 79Kr, in the light of a rotor plus one- and two-quasiparticle descriptions. Other previously reported low-spin states are also seen weakly with this reaction. Two new isomeric states of 9±1 ns at 337.8 keV and 84±8 ns at 227.6 keV are found. The latter decays into the 4+ isomer through a 46.8 keV transition, which lies unresolved from the 46.3 keV line. The existence of this doublet explains an earlier discrepancy.

Level structure of 80Rb studied with the 79Br(α, 3n) reaction☆

Abstract States of 80 Rb were excited through the 79 Br(α, 3n) reaction at bombarding energies between 30 and 55 MeV. Excitation functions, γ-ray angular distributions, γ-γ coincidences and γ-time distributions with respect to the beam bursts were determined. Levels with the following excitation energies (in keV) and spin-parity values are proposed: 175.6 2, 334.9 3 (−) , 375.9 3 + , 418.6 (4), 423.1 (4), 470.5, 472.5 4, 486.1 (5) and 496.4 (5). The 175.6, 375.9 and 472.5 keV levels together with the ground state exhibit a K π = 1 + quasi-rotational structure, regarding the energy spacings and the mixing ratios of the γ-rays. It is shown that this structure is quite similar to bands known in 68 Ga and 64 Cu. A description of these bands in terms of the Nilsson model gives satisfactory results.