Time-resolved spectroscopy of Al, Ti, and Mo X pinch radiation using an X-ray streak camera

Time-resolved spectroscopic measurements of the radiation emitted from Al, Ti, and Mo X pinches have been made with time resolution. The radiation is emitted from micropinch plasmas with sizes of order in times in the 10- range. Spectra implied that dense, plasmas were produced, such as a lifetime, 1.5- electron temperature and near solid-density Ti plasma. The experimental systems and analysis methods are described in detail, including line ratio calculations for μm-scale Ti and Al plasmas with ion densities of 10¹⁹-10²⁴ cm⁻³ and electron temperatures.     

The luminescence of Sm in alkaline earth borophosphates

The temperature-dependent luminescence of Sm²⁺ ions in MBPO₅ was studied. At low temperature, Sm²⁺ in this series shows 4f⁶→4f⁶ luminescence with only a single emission line observed for the transition, revealing that only one crystallographic cationic site is available for Sm²⁺ in all the hosts. With increasing temperature, the emission intensity of the transition increases whereas that of the transitions decreases. The transitions of Sm²⁺ were observed in BaBPO₅ and its intensity increases with increasing temperature. At , a broad band of the 4f⁵5d→4f⁶ luminescent transition of Sm²⁺ in SrBPO₅ and BaBPO₅ with maximum at appears due to the thermal population. The lifetime of the transition was recorded at different temperatures, showing a single exponential decay for Sm²⁺ in SrBPO₅ and BaBPO₅ but a non-single-exponential decay in CaBPO₅.     

Adsorption characteristics of atomic nitrogen on ruthenium surfaces

We have studied the adsorption, vibration, and diffusion of N atoms on Ru(0 0 0 1), , and surfaces by means of the 5-parameter Morse potential (5-MP) of interaction between atomic nitrogen and a metal surface. The adsorption sites, adsorption geometry, binding energy and eigenvibration of atomic nitrogen on the different ruthenium surfaces are calculated. It is shown that atomic nitrogen always preferably occupies the high coordination sites on Ru surfaces. The 4-fold site is the preferable adsorption site for atomic nitrogen on both open and surfaces while 3-fold site is the most stable adsorption site for atomic nitrogen on both Ru(0 0 0 1) and surfaces. Moreover, we find the lowest energy pathway of diffusion and diffusion barriers of atomic nitrogen on the surfaces.     

Giant intersubband polariton splitting in InAs/AlSb microcavities

The optical response of the intersubband excitation of multiple InAs/AlSb quantum wells embedded in a planar semiconductor microcavity has been studied through angle-dependent reflectance measurements. Using a resonator based on total internal reflection, a strong coupling is demonstrated between the intersubband optical transition and the cavity photon, with the attendant formation of intersubband polaritons. A giant vacuum-Rabi splitting 2Ω_R was observed both at liquid helium temperatures () as well as at 300 K (), for a transition energy . The observed ratio is a record high value (14%) for any strongly-coupled systems, and demonstrates the huge potential of this material for the achievement of the ultra-strong coupling regime predicted theoretically.     

Measurement of the 4d-photoionization cross section via two-photon and two-step excitation in sodium

We present a comparison of the photoionization cross sections of the 4d excited levels of sodium by using the two-step resonant laser excitation and by two-photon non-resonant excitation from the ground state. Dye lasers, pumped with a Nd: YAG laser, have been used in conjunction with a thermionic diode ion detector to measure cross sections and the atomic densities as a function of laser energy. By applying the saturation technique, the measured values of the cross sections and atomic densities for the 4d level by two-photon excitation are 12.2(2.4) Mb and , respectively. Where as in the case of two-step excitation, the cross section and number density for the 4d level via 3p level and for the 4d levels via 3p level are determined as 9.6(1.9) Mb, and 12.8(2.5) Mb, , respectively.     

Near-infrared diode laser spectroscopy of the HCSi radical

The , , and band spectra of HCSi radical were investigated by means of near-infrared diode laser spectroscopy to determine precise molecular constants for the and states. The detailed analysis of the rotationally resolved band spectra, studied for the first time in the present investigation, leads to the precise determination of molecular constants for the state associated with the Renner-Teller interaction. We obtained −0.15126663(53) and 495.00698(30) cm⁻¹ as the Renner-Teller parameter ε and the bending vibrational frequency ω₂, respectively. Based on the molecular constants for the and states, the rotational levels of the state were analyzed to obtain molecular constants and information on upper state perturbations. Using the available spectroscopic data, valence force fields for both the and states were estimated to aid in understanding the vibrational energy levels of the HCSi radical.     

Realization and field emission of CdSe nano-tetrapods with different arm lengths

The arms of CdSe nano-tetrapods can be greatly elongated with the core diameters and arm width unchanged by multiple injections. Room-temperature absorption and photoluminescence (PL) spectra of tetrapods with different arm lengths show that these tetrapods have almost the same core size, which is consistent with the high resolution TEM results. Field emission characteristics show that the onset field required drawing a current density of from CdSe nano-tetrapods with different arm lengths are , , and , respectively, and the field enhancement factors are determined to be about 218, 554, and 946, respectively. Results show that the longer is the arm of the tetrapods, the lower the turn-on field and the higher the field enhancement factor.     

Periodic boundary conditions and the correct molecular-dynamics ensemble

The use of periodic boundary conditions in molecular-dynamics simulations leads to the microcanonical ensemble of Ray and Zhang [J.R. Ray, H. Zhang, Phys. Rev. E 59 (1999) 4781] in which the total linear momentum and the generator of infinitesimal Galilean boosts are conserved quantities in addition to the total energy E, the volume V, and the number of particles N of the system. We find that the invariance of should be of importance in the analysis of ensemble averages of quantities that only depend on the spatial coordinate . As an application we study the density profile of an isolated system of hard disks with periodic boundary conditions in the absence of external forces. We find that the periodic boundary conditions give rise to an anomalous inhomogeneity in the density profile of the system. This inhomogeneity is only relevant for systems with a very small number of disks and is related to the conservation of the center of mass coordinates.