Charge topology of the coherent dissociation of relativistic <Superscript>11</Superscript>C and <Superscript>12</Superscript>N nuclei

The charge topology of coherent-dissociation events is presented for ¹¹С and ¹²N nuclei of energy 1.2 GeV per nucleon bombarding nuclear track emulsions. This topology is compared with respective data for ⁷Be, ^8,10B, ^9,10C, and ¹⁴N nuclei.     

Exposure of nuclear track emulsion to 8He nuclei at the ACCULINNA separator

Nuclear track emulsion is exposed to a beam of radioactive ⁸He nuclei with an energy of 60 MeV and enrichment of about 80% at the ACCULINNA separator. Measurements of 278 decays of the ⁸He nuclei stopped in the emulsion allow the potential of the α spectrometry to be estimated and the thermal drift of ⁸He atoms in matter to be observed for the first time.     

Heteromolecular structures in aqueous solutions of dimethylformamide and tetrahydrofuran,according to molecular dynamics data

The complex dielectric permittivity of aqueous solutions of tetrahydrofuran and dimethylformamide in wide ranges of temperature (220–300 K) and pressure (0.1–12 MPa) is studied by means of molecular dynamics. The autocorrelation functions of the dipole moments of molecules are calculated. Dielectric permittivity spectra are obtained. The dielectric relaxation times are determined as functions of the tetrahydrofuran and dimethylformamide concentrations in the indicated binary mixtures. The dielectric relaxation frequency shifts toward low frequencies in the range of tetrahydrofuran and dimethylformamide concentrations x ≤ 0.5 molar fraction, due to the formation of heteromolecular structures with hydrogen bonds. This is confirmed by the negative values of the excess dielectric permittivities of binary solutions at x ～ 0.3–0.4 molar fraction.     

Mastering the molecular dynamics of a bistable molecule by single atom manipulation

At low temperature (5 K), a single biphenyl molecule adsorbed on a Si(100) surface behaves as a bistable device which can be reversibly switched by electronic excitation with the scanning tunneling microscope tip. Density functional theory suggests that the biphenyl molecule is adsorbed with one dissociated hydrogen atom bonded to a neighbor surface silicon atom. By desorbing this hydrogen atom with the STM tip, the interaction of the molecule with the surface is modified such that it becomes transformed into a multistable device with four stable states having switching yields increased by almost 2 orders of magnitude.     

Study of the Involvement of <Superscript>8</Superscript>Be and <Superscript>9</Superscript>B Nuclei in the Dissociation of Relativistic <Superscript>10</Superscript>C, <Superscript>10</Superscript>B,and <Superscript>12</Superscript>C Nuclei

The results obtained by estimating the contribution of 8Be and 9B nuclei to the coherent dissociation of ¹⁰C, ¹⁰B, and ¹²C relativistic nuclei in nuclear track emulsions (“white” stars) are presented. The selection of white stars accompanied by 9B leads to a distinct peak appearing in the distribution of the excitation energy of 2α2p ensembles and having a maximum at 4.1 ± 0.3 MeV. A 8Be nucleus manifests itself in the coherent-dissociation reaction ¹⁰B → ²He + H with a probability of (25 ± 5)%, (14 ± 3)% of it being due to 9B decays. The ratio of the branching fractions of the ⁹B + n and ⁹Be + p mirror channels is estimated at 6 ± 1. An analysis of the relativistic dissociation of ¹²C nuclei in a nuclear track emulsion revealed nine 3α events corresponding to the Hoyle state.     

Water at hydrophobic substrates: curvature, pressure, and temperature effects

We studied the water density profile close to spherical and planar hydrophobic objects using molecular dynamics (MD) simulations. For normal pressure and room temperature, the depletion layer thickness of a planar substrate is approximately 2.5 Angstroms. Even for quite large spherical solutes with a radius of R = 18 Angstroms, the depletion layer thickness is reduced by 30%, which shows that substrate curvature and roughness is an experimentally important factor. Rising temperature leads to a substantial increase of the depletion layer thickness. The compressibility of the depletion layer is found to be surprisingly small and only approximately 5 times higher than that of bulk water. A high electrostatic surface potential of 0.5 V is found, which presumably plays an important role in the presence of charged solutes, since it can promote adsorption into the interfacial layer.     

Dissociation of 10C nuclei in a track nuclear emulsion at an energy of 1.2 GeV per nucleon

The charge topology in the fragmentation of ¹⁰C nuclei in a track nuclear emulsion at an energy of 1.2 GeV per nucleon is studied. In the coherent dissociation of ¹⁰C nuclei, about 82% of events are associated with the channel ¹⁰C → 2α+ 2p. The angular distributions and correlations of product fragments are presented for this channel. It is found that among ¹⁰C → 2α+ 2p events, about 30% are associated with the process in which dissociation through the ground state of the unstable ⁹Be_g.s. nucleus is followed by ⁸Be_g.s. + p decays.     

Exposure of nuclear track emulsion to a mixed beam of relativistic 12N, 10C, and 7Be nuclei

A nuclear track emulsion was exposed to a mixed beam of relativistic ¹²N, ¹⁰C, and ⁷Be nuclei having a momentum of 2 GeV/c per nucleon. The beam was formed upon charge exchange processes involving ¹²C primary nuclei and their fragmentation. An analysis indicates that ¹⁰C nuclei are dominant in the beam and that ¹²N nuclei are present in it. The charge topology of relativistic fragments in the coherent dissociation of these nuclei is presented.