Neutron very cold neutrons

Amorphous ice has been studied in some detail by both X-ray and neutron diffraction [738-740]. The O- -O pair-correlation functions are similar to those of liquid water, except that on condensing on very cold surfaces, i.e., 10 K, there is an extra sharp peak at 3.3 A. This indicates some interpenetration of the tetrahedral disordered ice-like short-range structures. It appears that none of the many proposed atom-atom potential energy functions can simulate a structure for liquid water that predicts pair-correlation functions which are a satisfactory fit to the experimental data [741, 742]. Opinions seem to differ as to whether the discrepancy is in the theory or the experiments. 

SANS has historically been the domain of cold neutrons on reactor based sources, and impressive instrumentation, such as notably D22 at the Institute Laue Langevin, is currently available. The more recent emergence of neutron reflectivity as a probe of surface structure has been very much linked to the development of pulsed neutron sources and much of the initial impact of this technique has arisen from pulsed source instrumentation, such as the CRISP and SURF reflectometers at ISIS. - ... 

Early in the development of the theory of nucleosynthesis, an alternative to the high-T r-process canonical model (Sects. 7.1 and 7.2) has been proposed [63], It relies on the fact that very high densities (say p > 1010 gem-3) can lead material deep inside the neutron-rich side of the valley of nuclear stability as a result of the operation of endothermic free-electron captures, this so-called neutronisation of the material being possible even at the T = 0 limit. The astrophysical plausibility of this scenario in accounting for the production of the r-nuclides has long been questioned, and has remained largely unexplored until the study of the composition of the outer and inner crusts of neutron stars and of the decompression of cold neutronised matter resulting from tidal effects of a black hole on a neutron-star companion ([24] for references). The decompression of cold neutron star matter has recently been studied further (Sect. 9). 

As reminded in Sect. 7.3, the decompression of the crust of cold neutron stars (NSs) made of a lattice of very neutron-rich nuclei immersed in a gas of neutrons and degenerate electrons has long been envisioned as a possible site for the development of a high-density r-process (HIDER). This decompression could result from the coalescence of two NSs or of a NS and a black hole (BH) in a binary system. It could also result from the ejection of material from magnetars. 

It can be inferred from O Eq. (6.13) that strongly coupled plasmas tend to be cold and dense, whereas weakly coupled plasmas are diffuse and hot. Examples of strongly coupled plasmas include solid-density laser ablation plasmas, the very "cold (i.e., with kinetic temperatures similar to the ionization energy) plasmas found in "high pressure arc discharges, and the plasmas which constitute the atmospheres of collapsed objects such as white dwarfs and neutron stars. On the other hand, the hot diffuse plasmas - typically encountered in ionospheric physics, astrophysics, nuclear fusion, and space plasma physics — are invariably weakly coupled. 

In any case this is a very small effect when compared to Fig. 5a where the intensity at 150 meV is more than 130 times bigger. It shows that even with cold neutrons (E = 3.1 meV) one can observe peaks around 150 meV when the background is low as it is on the IN6 spectrometer. 

The behavior of hehum at low temperatures is quite different from that of all other materials. When cooled under atmospheric pressure, helium liquefies at 4.2 K, but it never solidifies, no matter how cold it is made. This behavior is inejqrlicable in terms of classical physics where, at a sufficiently low temperature, even the very weak interatomic forces that exist between helium atoms should be sufficient to draw the material together into a crystalline solid. Furthermore, the liquid in question has maity extraordinary properties. In particular, it undergoes a transition at 2 K to a state of superfluidity, such that it has zero viscosity and can flow without dissipation of energy, even through channels of vanishingly small dimensions. This frictionless flow of the liquid is closely analogous to the frictionless flow of the electrons in a superconductor. On Earth, superfluidity and superconductivity are exclusively low-temperature phenomena, but it is inferred that they probably also arise in the proton and neutron fluids within neutron stars. 

Universe, tell me how old you are, and 1 will tell you the colour of your radiation background and the energy of each of your photons. Today, the cosmic background radiation is red, very red. It is so red and cold (about 3 K) that it cannot be seen. Its chilled voice quivers in the great ears of our radiotelescopes. Solar emissions, on the other hand, can be compared with the radiation from an incandescent body at a temperature of around 5700 K. Temperatures vary across the Universe, from 2.73 K for the cosmic background to 100 billion K when a neutron star has just emerged. 

Properties Hard, lustrous, grayish, crystalline scales or gray amorphous powder. D 6.4, mp 1850C, bp 4377C. Soluble in hot, very concentrated acids insoluble in water and cold acids. Corrosion resistant, low neutron absorption. 

In view of the renewed interest for a high-density r-process, a simple steady flow model, referred to in the following as HIDER, may be developed. Irrespective of the specific details of a given astrophysical scenario, it allows to follow in a very simple and approximate way the evolution of the composition of an initial cold (say T = 0) highly neutronized matter under the combined effect of /3-decays and of the captures of free neutrons that are an important initial component of the considered material. These are the only two types of transformations that have to be considered if fissions are disregarded, and if... 

The transuranium elements up to 106 were synthesized by accelerating neutrons or very light nuclei into other actinides including costly, unstable artificial elements such as californium (98). In 1973, Yuri Oganessian (1933- ) and Alexander G. Demin in Dubna developed the concept of soft fusion or cold fusion (not to be confused with the unrelated cold fusion debacle of 1989) which they successfully... 

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