Giuseppe Longo

• University of Bologna

Cheko, a small lake located in Siberia close to the epicentre of the 1908 Tunguska explosion, might fill a crater left by the impact of a fragment of a Cosmic Body. Sediment cores from the lake’s bottom were studied to support or reject this hypothesis. A 175-cm long core, collected near the center of the lake, consists of an upper ∼1 m thick seque...

Finding a piece of the elusive cosmic body that devastated a Siberian forest a century ago could help save the earth in the centuries to come

Several lines of evidence were presented in Gasperini et al. [Terra Nova (2007), vol. 19, pp. 245–251] suggesting that Lake Cheko, a small lake close to the alleged epicentre of the 1908 Tunguska Event, might be a secondary impact crater. Collins et al. [Terra Nova (2008), this volume] argue against this hypothesis. We reply here arguing in favour...

The so-called ‘Tunguska Event’ refers to a major explosion that occurred on 30 June 1908 in the Tunguska region of Siberia, causing the destruction of over 2000 km2 of taiga, globally detected pressure and seismic waves, and bright luminescence in the night skies of Europe and Central Asia, combined with other unusual phenomena. The ‘Tunguska Event...

It is shown that predictions of the direct-semidirect model together with high-energy resolution data from radiative capture measurements with polarized neutrons can assist in obtaining information about the location, multipolarity, width and strength of giant multipole resonances.

The direct-semidirect model is used to investigate the sensitivity of polarized neutron capture to the final-state j value (j = l ± ½) for a given l. It is shown that predictions of the model together with data from polarization measurements can be useful as a tool both in assigning j-values to final states and in obtaining information about giant...

Longo G.: "The Tunguska event" . Chapter 18, pp. 303-330 in the book: "Comet/Asteroid Impacts and Human Society, An Interdisciplinary Approach, Bobrowsky, Peter T.; Rickman, Hans (Eds.)." , 546 p., © Springer-Verlag, Berlin Heidelberg New York, 2007 In the early morning of 30th June 1908, a powerful explosion over the basin of the Podkamennaya Tu...

A multidisciplinary investigation of the Tunguska site (Central Siberia) devastated in 1908 by the explosion of a cosmic body has been carried out in July 14-29, 1999 by the Tunguska99 expedition (see http://www-th.bo.infn.it/tunguska/). In this framework, the remote sensing of a 300-km2 territory has been performed in collaboration with the Russia...

A multidisciplinary investigation of the Tunguska site has been carried out in July 14-29, 1999 by the Tunguska99 expedition. In this framework, the remote sensing of a 300-km2 area near the explosion epicenter has been performed. The photos have been taken in the scale 1:8000 and 1:14000. In parallel, a line scanner made simultaneously a survey in...

The complete characterisation of the Tunguska event of 30th June 1908 is still a challenge for astrophysicists. We studied the huge amount of scientific literature to select data directly available from measurements and we introduced parameters calculated by the application of models, and evaluated other possibilities. We then selected a range of m...

The Tunguska event is the largest cosmic calamity caused by the impact of an interplanetary body with the Earth atmosphere that happened during historical times. A two-week scientific expedition (Tunguska99, http://www-th. bo. infn. it/tunguska/) to the impact site has been carried out starting from 14 July 1999 by the Department of Physics of the...

We studied the available scientific literature on the Tunguska event of 30 June 1908 to obtain parameter sets of the Tunguska Cosmic Body atmospheric dynamics. We performed a comparative analysis by means of available theoretical models and with the help of interplanetary dynamics, and we excluded unphysical orbits. Our results indicate a very high...

After a brief summary of the results obtained up to now by a world wide survey of the Environmental Radiation, we discuss the possibility of operating a compact scintillation NaI(TI) detector at the Chacaltaya Cosmic Ray Laboratory in order to monitor with continuity the low energy secondary cosmic radiation and radioactivity, airborne and from env...

We performed a detailed analysis of the large amount of the literature on the Tunguska event in order to determine a useful sample of the observed data. Then from a selected range of meaningful atmospheric trajectories, we computed a set of 886 possible TCB (Tunguska Cosmic Body) orbits, which were used to estimate the probabilities of the possible...

We studied the available scientific literature on the Tunguska event of 30 June 1908 to select a sample of atmospheric trajectories. Then we calculated a set of parameters from which we obtained 886 orbits. Using the method of Bottke and colleagues, based on dynamical properties of celestial bodies, we estimated the probabilities of different origi...

For more than one year a detector for environmental radiation (airborne radionuclides and cosmic rays) has been operated at the Italian base in the Arctic. We report here on time variations of the cosmic ray component in the energy range 3-18 MeV and compare them with observations made by neutron monitor stations at different latitudes.

We performed an integrated acoustic and GPR study of the Cheko Lake area (101 o E, 62 o N) during summer 1999. The GPR study aimed at imaging lake bottom and shallow sedimentary layers to plan coring of sediments coeval with the catastrophic 1908 explosion. The water of the Cheko Lake strongly attenuates radar waves. Therefore, the central and nort...

We performed an integrated acoustic and GPR study of the Cheko Lake area (101 o E, 62 o N) during summer 1999. The GPR study aimed at imaging lake bottom and shallow sedimentary layers to plan coring of sediments coeval with the catastrophic 1908 explosion. The water of the Cheko Lake strongly attenuates radar waves. Therefore, the central and nort...

In July 14-30, 1999 an Italian scientific expedition was carried out in Tunguska (Siberia), the region of the 1908 explosion of a cosmic body. The main tasks of the expedition were: 1) to study the structure and sediments of Cheko, a small lake located near the epicenter of the Tunguska event; 2) to carry out an aerial photosurvey of the explosion...

An expedition to the Tunguska crater to look for witnesses of the catastrophe in trees.

It has been found that in the resin of trees that have survived the Tunguska catastrophe, the quantity of microsized particles trapped at the moment of the event varies markedly from one site to another. The high density of particles found in the trees close to the epicenter may be an experimental point in favor of the fragmentation model recently...

A new method is used here to obtain experimental data on the nature and composition of the Tunguska Cosmic Body. The leading hypothesis of the method is that in the forest conifers which have survived the Tunguska catastrophe, the fluid resin present at the moment of the event could have acted as a trap for airborne particles, as happens in amber....

In recent years important steps have been taken in improving East-West relations and in building meaningful accords to control and reduce different categories of weapons. It seems, nevertheless, that the new political climate is insufficient to give productive results as far as naval weapons are concerned. The United States and the Soviet Union, as...

A collection of papers that were the result of meetings held in Italy under the auspices of the International School on Disarmament and Research on Conflicts (ISODAROC). The primary aim of the meetings was to explore the prospects for space and nuclear weaponry in the coming decade.

The differential cross section for the production of high-energy γ-rays (10-50 MeV) due to radiative capture of fast neutrons by Ti and Ni, are calculated by means of the direct-semidirect (DSD) model.

Spectra of high-energy photons following the radiative capture of 8-22 MeV protons in 110Cd and 111In are measured. The (p, gamma) differential cross sections at 90° with respect to the beam axis is deduced from the integration of measured spectra. The photon angular distribution is measured for the 110Cd(p, gamma0) reaction, too, at 13 MeV inciden...

Angular distributions in photonucleon and nucleon radiative capture reactions are investigated by means of the direct-semidirect model. It is shown that the introduction of higher-order multipoles and the choice of an appropriate coupling interaction allow reproduction of experimental data without recourse to free parameters.

The direct-semidirect model for dipole and quadrupole fast nucleon radiative capture is applied to calculate angular distributions of emitted photons. It is shown how the model can supply a valuable aid in analysing angular distribution data and obtaining indications as to the presence of isoscalar and isovector giant quadrupole resonances.

The interference between dipole and quadrupole radiative capture of fast nucleons is investigated on the basis of the direct-semidirect model. It is shown how the use of contour maps of the interference factor here introduced can be a valuable tool in indicating the more appropriate energy-angle areas for investigating the presence ofE2-collectivit...

The radiative capture of 5-50 MeV nucleons is investigated taking into account isoscalar and isovector quadrupole contributions. For incident energies greater than 20 MeV, similar cross section values are obtained for E2 capture both of neutrons and of protons, though the dominant capture mechanisms are different.

Information on the production of high-energy photons, due to (n, gamma ) reactions for neutron energies up to about 20 MeV, may be useful in fusion reactor technology. Use of theoretical estimates is required to make up for the lack of measured data. For this purpose, the semidirect capture model is used. The model is refined by introducing a volum...

Activation radiative-capture cross sections of 14.6-MeV neutrons in ²⁷Al, ⁵⁰Ti, ⁵¹V, ¹⁰³Rh, ¹²⁷I, and ¹³⁹La have been measured to check and extend to other nuclei recent improved activation measurements. The measured activities strongly depend on the target-head material, on the tritium target backing and on the sample thickness, whose influence is...

Gamma-ray spectra following the capture of 14 MeV neutrons by Si, Sr, Ce and208Pb are compared with the predictions of semi-direct theory. All the values for the input parameters are taken from experimental data independent of the γ-ray experimental spectra examined. It is found that for nuclei in different mass regions the volume form of the coupl...

A coupling interaction between the nucleon and the nuclear E1 mode having a volume radial form instead of the usual surface one is used in the semi-direct nucleon radiative-capture theory. The calculated cross sections for the 208Pb(n,γ) and 142Ce(p,γ) reactions in the giantresonance region reproduce the measured ones both in shape and magnitude. S...

The semi-direct nucleon radiative capture cross-section is calculated using a colume radial form factor for the particle-vibration coupling instead of the previous surface form factor. A significant improvement in the agreement between theory and experiment is thus obtained.

Spectra of high-energy photons from the radiative capture of 14.06 MeV neutrons in 133Cs, 139La, Ce and 159Tb are recorded by means of a time-of-flight spectrometer. The (n,γ) cross sections, deduced from the integration of measured spectra, are very close for the four nuclei considered. The value of the159Tb (n, γ) cross section obtained from the...

Gamma-ray spectra from the radiative capture of 14.06 MeV neutrons in 59Co, 93Nb and 103Rh are measured by means of a time-of-flight spectrometer. The (n, gamma) cross sections, deduced from the integration of measured spectra, are very similar for the three nuclei considered. The value of the 103Rh(n, gamma) cross section obtained here is lower by...

Gamma-ray spectra from the radiative capture of 14.06 MeV neutrons in natural Si, Rb, Sr and Y are investigated. The time-of-flight method is used to discriminate photons from scattered neutrons and to obtain about a 20 keV energy spread of incident neutrons. These results are compared with the theoretical predictions of direct and collective captu...

Summary For each transition of the208Pb(p, γ) and208Pb(n, γ) reactions the partial direct and collective cross-sections are obtained for (6÷30) MeV nucleon energies. The radial, energy and angular momentum dependence of matrix elements is investigated and explained by means of considerations on the Coulomb and the centrifugal repulsion influences....

1. In July 14{30, 1999 an Italian scientiic expedition was carried out in Tunguska (Siberia), the region of the 1908 explosion of a cosmic body (see Di Martino, M. et al., 1998, and references therein). The expedition, named "Tunguska99", was organized by the Department o f P h ysics of the University of Bologna, in collabora-tion with the Turin As...

Information on the production of high-energy photons, due to (n,..gamma..) reactions for neutron energies up to approximately 20 MeV, may be useful in reactor technology. Use of theoretical estimates is required to make up for the lack of measured data. For this purpose, the semidirect capture model is used. The model is refined by introducing a vo...

The knowledge of the correct values of (n,..gamma..) cross sections for high energy neutrons is of great interest for studies into nuclear reaction mechanism as well as for reactor shielding purposes and in particular fusion-reactor design. The use of theoretical estimates is therefore required to fill the gaps in the available experimental data. F...

The solution of a neutron multiple scattering problem is obtained by using a quantal approach. The elastic isotropic scattering is considered in the approximation where the scattering length is much less than both the neutron mean free path and the average distance between nuclei. In the case of a finite thickness slab, the probability density of t...

An expression of the cross-section for the quadrupole radiative capture of nucleons by nuclei via direct mechanism is given. The142Ce(p, γ) reaction is investigated in the (10÷50) MeV energy range. It is shown that for proton energies above 20 MeV the quadrupole contribution to the cross-section may be of the same order of magnitude as the dipole o...

A systematic analysis is carried out to test the validity of the direct andcollective mechanisms for the neutron radiative capture by nuclei in a wide range of mass number. It is found that the two processes can reasonably explain the experimental (n, gamma) cross sections of heavy nuclei (A > 40) with magic or near-magic neutron number in the (10-...

The interference term between direct and collective dipole radiative capture of nucleons by nuclei is obtained. The cross-section is written in a Breit-Wigner form as a sum of three terms: direct capture, collective or « resonant » capture and interference term. The expression of the latter term is investigated and the conditions for constructive,...

Summary The expression for the nucleon radiative capture cross-section by nuclei via a collective mechanism is completed in order to take into account the spin-orbit interaction. The direct and collective cross-sections for208Pb(n, γ) and208Pb(p, γ) reactions are calculated. A good agreement between calculated and measured cross-sections is obtaine...

1] The results of the environmental radiation (ER) monitoring obtained during the Tunguska expedition of July 1999 with a NaI(Tl) scintillation detector are reported. Some interesting meteorological effects related to the airborne radioactive components (radon and thoron decay products) have been observed. The main effects observed are (1) the doub...