Multiple pulse passive mode locking in lasers with spectrally inhomogeneous gain

A new mechanism of formation of multiple pulse operation, multistability, and hysteresis in lasers with spectrally inhomogeneous gain media such as ion-doped glasses has been discovered. The multistability manifests itself as a dependence on the initial conditions of the number of pulses in the laser operation that is established after the transient process. It has been found that the dependence of the number of pulses in the established operation on the pumping power is hysteretic in character. The mechanism revealed is connected with a change in the frequency dispersion of the active medium caused by the spectrally inhomogeneous saturation of the gain. Analysis and numerical simulation have been carried out on the basis of the modified Ginzburg-Landau equation, which takes into account the change in the spectral profile of the gain during laser operation.     

Refinement of molecular constants of neodymium triiodide by electron diffraction

The molecular structure of neodymium triiodide has been studied by electron diffraction. The molecule has D_3h symmetry; the equilibrium intemuclear distance is R_e(Nd-I) = 286.6(5) pm. The deformation frequencies are estimated from the experimental mean square vibration amplitudes and stretching frequencies. Translated from Zhurnal Strukturnoi Khimii, Vol. 41, No. 4, pp. 725-729, July-August, 2000     

Single-ion-beam experimental setup for combined implantation and deposition

Technical Physics - An original approach and a single-ion-beam experimental setup for in situ ion implantation combined with the deposition of various materials on metals are suggested. The...     

Reversible Switching between Highly Porous and Nonporous Phases of an Interpenetrated Diamondoid Coordination Network That Exhibits Gate‐Opening at Methane Storage Pressures

Herein, we report that a new flexible coordination network, NiL₂ (L=4‐(4‐pyridyl)‐biphenyl‐4‐carboxylic acid), with diamondoid topology switches between non‐porous (closed) and several porous (open) phases at specific CO₂ and CH₄ pressures. These phases are manifested by multi‐step low‐pressure isotherms for CO₂ or a single‐step high‐pressure isotherm for CH₄. The potential methane working capacity of NiL₂ approaches that of compressed natural gas but at much lower pressures. The guest‐induced phase transitions of NiL₂ were studied by single‐crystal XRD, in situ variable pressure powder XRD, synchrotron powder XRD, pressure‐gradient differential scanning calorimetry (P‐DSC), and molecular modeling. The detailed structural information provides insight into the extreme flexibility of NiL₂ . Specifically, the extended linker ligand, L , undergoes ligand contortion and interactions between interpenetrated networks or sorbate–sorbent interactions enable the observed switching.     

Adaptive Chemical Networks under Non‐Equilibrium Conditions: The Evaporating Droplet

Non‐volatile solutes in an evaporating drop experience an out‐of‐equilibrium state due to non‐linear concentration effects and complex flow patterns. Here, we demonstrate a small molecule chemical reaction network that undergoes a rapid adaptation response to the out‐of‐equilibrium conditions inside the droplet leading to control over the molecular constitution and spatial arrangement of the deposition pattern. Adaptation results in a pronounced coffee stain effect and coupling to chemical concentration gradients within the drop is demonstrated. Amplification and suppression of network species are readily identifiable with confocal fluorescence microscopy. We anticipate that these observations will contribute to the design and exploration of out‐of‐equilibrium chemical systems, as well as be useful towards the development of point‐of‐care medical diagnostics and controlled deposition of small molecules through inkjet printing.     

Galvanomagnetic properties of thin films of bismuth and bismuth–antimony alloys on substrates with different thermal expansions

Temperature dependences of the galvanomagnetic properties of films of bismuth and Bi_{100 – x}Sb_x (x ≤ 12) on substrates with different temperature expansion coefficients were studied in the temperature range of 77–300 K. The block films were prepared through thermal deposition, and single-crystal Bi_{100 – x}Sb_x were grown by zone recrystallization under a coating. It was found that the temperature expansion coefficient of a substrate substantially influenced the galvanomagnetic properties of Bi and Bi_{100 – x}Sb_x films. Using the experimental data, the change in the charge-carrier concentration in the Bi and Bi_{100 – x}Sb_x films on different substrates at 77 K was estimated.     

Enumeration of melting diagrams of ternary reciprocal systems without continuous solid solutions

The topological properties were considered for melting diagrams of ternary reciprocal systems with constant-composition phases or limited solid solutions. Relations between the topological parameters of the diagrams were found. Algorithms for solving problems of generation of liquidus surface schemes and their enumeration and classification were presented.     

Experimental study of the speed of sound in liquid and gaseous refrigerant R-407C

The speed of sound in liquid and gaseous refrigerant R-407C was measured by the method of ultrasonic interferometer in the temperature range from 293 to 373 K and pressure from 0.05 to 0.5 to 3.7 MPa. The experimental uncertainties of the temperature, pressure, and speed of sound measurements were estimated to be within ±20 mK, ±4 kPa, and ±(0.1–0.3) %, respectively. The obtained results are compared with the calculated speed of sound from the fundamental state equation for the Helmholtz free energy.     

The Cubic Superstructure-I of Tetrabutylammonium Fluoride (C4H9)4NF·29.7H2O Clathrate Hydrate

The crystal structure of (C₄H₉)₄NF·29.7H₂O clathrate hydrate (ionic clathrate) determined by X-Ray analysis is reported. The structure is cubic, I $\overline 4 3dThe crystal structure of (C₄H₉)₄NF·29.7H₂O clathrate hydrate (ionic clathrate) determined by X-Ray analysis is reported. The structure is cubic, I , a = 24.375(3) ? (150 K). Its idealized water framework is analogous to that of cubic structure-I of gas hydrates but with eight-fold unit cell, that is a superstructure of cubic structure-I. This is the last structure found in the binary system (C₄H₉)₄NF–H₂O which was not characterized by X-ray analysis earlier. The structure features of the compound under investigation and others existing in H₂O–(C₄H₉)₄NF binary system are discussed.