Pleiades Publishing Ltd

It is observed that the photoexcitation efficiency of neutral long-lived states in a trans-polyacetylene chain increases with increasing photon energy of the excitation. The observed effect is given an interpretation according to which the energy of a photon above the optical absorption edge is added to the excitation of the vibrational subsystem, increasing sharply the probability that the chain relaxes into a long-lived deformed neutral state.

An expression is obtained for the reflection coefficient of circularly polarized light normally incident on the film of a cholesteric liquid crystal with a variable helix pitch. It is shown that, in the case of a single defect (local change in the helix pitch), the spectrum of light reflection from a cholesteric acquires a dip corresponding to the defect mode. New qualitative features appear in the reflection spectrum of a cholesteric with two defects as the distance between them varies.

The spectra of magnetoplasma excitations in two-dimensional electron disks and rings are studied by optical detection of resonance microwave absorption. For ring-shaped structures, two types of edge magnetoplasma modes localized along the inner and outer boundaries of the ring are observed. It is shown that the interaction between these modes leads to a strong modification of their magnetic-field dependences as compared to disks. In addition to the longitudinal edge magnetoplasma excitations, transverse plasma modes associated with the electron density oscillations along the ring radius are revealed. The spectra of magnetoplasma excitations are calculated in terms of the electrodynamic theory for both ring-shaped and disk-shaped structures. The classification of all modes of collective magnetoplasma excitations observed in the experiment is performed on the basis of the comparison between experimental and theoretical results.

Chúng tôi thảo luận về thước đo hiệu quả mà chế độ Nambu–Goldstone trải nghiệm khi lan truyền trong trạng thái siêu lỏng spin bẻ gãy đối xứng của sự chuyển động đồng bộ của từ hóa. Chế độ tập thể này đại diện cho phonon trong ngưng tụ Bose–Einstein (BEC) của các magnón quang điều khiển bằng sóng RF hoặc bùng phát không cân bằng. Chúng tôi rút ra năng lượng tự do BEC hiệu quả và xem xét phổ phonon khi BEC siêu lỏng spin được hình thành trong pha cực phân cực không đồng nhất của 3He siêu lỏng, đã được quan sát thực nghiệm trong các mẫu 3He trong aergel đơn trục. Sự chuyển động đồng bộ của từ hóa gặp phải một sự không ổn định tại một giá trị krit cao của góc nghiêng của trường từ bên ngoài so với trục độ lệch. Từ hành động của sự sai lệch bậc hai quanh điểm cân bằng, sự không ổn định này được hiểu như là một sự thay đổi ký hiệu từ Minkowski sang Euclid của thước đo phonon hiệu quả. Chúng tôi cũng lưu ý sự tương đồng giữa BEC magnón trong vùng không ổn định và một ngưng tụ "ma" vô hướng hiệu quả.

KMnO4 has unusual formal manganese oxidation state Mn+7 that seems puzzling: the energy of creating such ion (119 eV) is much greater than the energy of chemical bonds (up to ~10 eV). We have used the Wannier functions formalism to analyze the distribution of Mn- $$3d$$ electrons and O- $$2p$$ electrons for empty electronic states in the $${\text{MnO}}_{4}^{ - }$$ complex and have found that, while formally one has $${{d}^{0}}$$ configuration for manganese ion in this compound, in reality only about one-half of the hole density described by these Wannier functions corresponding to this configuration belongs to d-electrons, while the other half is spread over surrounding oxygen atoms. This corresponds much more to Mn+7 state than to Mn+2, because the calculated total number of d‑electrons is equal to 5.25. Our analysis has also sown nearly perfect covalent type of chemical bond within the $${\text{MnO}}_{4}^{ - }$$ complex with negligible contribution of the ionic part.

The excitation of stimulated scattering of laser radiation at several equidistant frequencies is observed in an aqueous suspension of hollow glass microspheres. The scattering spectrum is frequency-asymmetric. No stimulated Brillouin scattering, accompanying nonlinear processes in condensed media excited by narrowband laser pulses on the order of tens of nanoseconds, is detected. The observed features are interpreted in terms of stimulated scattering mediated by the whispering-gallery modes of glass microspheres.

We present large scale electronic structure based molecular dynamics simulations of liquid methane at planetary conditions. In particular, we address the controversy of whether or not the interior of Uranus and Neptune consists of diamond. In our simulations we find no evidence for the formation of diamond, but rather sp 2-bonded polymeric carbon. Furthermore, we predict that at high temperature hydrogen may exist in its monoatomic and metallic state. The implications of our finding for the planetary models of Uranus and Neptune are in detail discussed.

The voltage response of a thin-film normal-metal hot-electron bolometer based on a SINIS (superconductor-insulator-normal metal-insulator-superconductor) structure to the radiation of a high-temperature Josephson junction in the terahertz frequency region was measured. Bolometers were integrated with planar log-periodic and double-dipole antennas, and Josephson junctions were integrated with log-periodic antennas. Measurements showed that the Josephson junction at a temperature of 260 mK was overheated by the transport current, so that its electron temperature exceeded 3 K at a bias voltage of 1 mV. The maximum response of a bolometer with a double-dipole antenna was observed at a frequency of 300 GHz, which agreed well with the calculated value. The Josephson radiation was observed at frequencies up to 1.7 THz. The voltage response of a bolometer reached 4×108 V/W, and the total noise-equivalent power reached 1.5×10−17 W/Hz1/2.