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.     

MRCI studies on the electronic structure of AlN and AlN, and the electron affinity of AlN

Using multireference configuration-interaction methods and double to triple-zeta basis sets with semidiffuse and polarization functions, potential energies and spectroscopic constants for low-lying doublet, and quartet states of AlN⁻ were calculated. has R_e=3.280 bohr and . lies 0.17 eV above the ground state. Using an estimated electron affinity of 2.1 eV for AlN, four states of AlN⁻ are found to be stable, namely , , , and . Comparisons with the isovalent anions BN⁻ (three stable states) and AlP⁻ (seven stable states) are made. Photo-detachment of an electron from the state of AlN⁻ can lead to an accurate determination of the energy difference between the two close-lying lowest states of AlN, and , predicted here to be 0.09 eV apart.     

Ab initio calculation of electronic transition moments for singlet excited states of the H2 molecule

Ab initio CI electronic dipole transition moments have been calculated for the transitions between singlet states of the hydrogen molecule correlating asymptotically with H(nl)+H(1s) (n=1,2,3). The investigated singlet-singlet transitions include the 30 (n=3) inter-Rydberg transitions and the 32 transitions which may contribute to absorption in the far wings of the Balmer α line of atomic hydrogen perturbed by another hydrogen atom in its ground state. Results are presented for internuclear distances 1.0a₀?R?12a₀. The present results compare well with the previous theoretical calculations available for about half of the transitions treated in the present work. Thirty eight new transitions are presented. Adiabatic potential energies for the and and improved energies for the and states are reported as well.     

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.     

Vibronic transition moments and line intensities for H2O

Ab initio calculations of the electronic dipole moment components for the and electronic states and the electronic transition moment for the - transition of H₂O⁺ have been carried out. Parameterized analytical functions have been fitted through the computed ab initio data points, and the resulting dipole moment and transition moment surfaces have been used, along with potential energy surfaces derived from the ab initio results of Brommer et al. [J. Chem. Phys. 98 (1993) 5222], to simulate H₂O⁺ spectra and to generate an extensive set of vibronic transition moments for the and band systems of H₂O⁺. The work is made with the dual purpose of facilitating further assignments of high-resolution spectra [J. Mol. Spectrosc. 219 (2003) 258] and of allowing cometary spectra of H₂O⁺ to be simulated [Ap. J. 574 (2002) L183].     

Maximising rovibrational assignments in the ν1 band of NSCl by spectral analysis by subtraction of simulated intensities (SASSI)

The ν₁ band of thiazyl chloride (NSCl) has been measured by high resolution FTIR spectroscopy, and studied using the spectral analysis by subtraction of simulated intensities (SASSI)-technique. This involves assignment and fitting of a component, creating a global simulation of the entire component to be subtracted from the experimental spectrum, and subsequent analysis of the resultant spectrum. Through this iterative procedure it has been possible to assign rovibrational transitions for seven components, with populations in the lower vibrational state as low as 2% of the total. The components are the fundamental and , , and hotbands of ¹⁴N³²S³⁵Cl, the fundamental and hotband of ¹⁴N³²S³⁷Cl, and the fundamental of ¹⁴N³⁴S³⁵Cl. Rotational and centrifugal distortion constants beyond the quartic level have been obtained by fitting to Watson’s A-reduced Hamiltonian in upper and lower states.     

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.     

First-principles study of arsenic impurity clusters in molecular beam epitaxy (MBE) grown HgCdTe

The understanding of the microstructures of the arsenic tetramer , dimer , and singlet of HgCdTe is important to explain the high electrical compensation of molecular beam epitaxy (MBE) samples and the conversion to p-type behavior. The stable configurations were obtained from the first-principles calculations for the arsenic cluster defects [ (n=1, 2, and 4)] in as-grown HgCdTe. According to the defect formation energies calculated under Te-rich conditions, the most probable configurations of , , and have been established. For the optimized and the energy is favorable to combine in a nearest neighboring mercury vacancy , and the corresponding configurations can be used to explain the self-compensated n-type characteristics in as-grown materials. is likely to be more abundant than in as-grown materials, but arsenic atoms are more strongly bounded in than in , thus more substantial activation energy is needed for than that for . The atomic relaxations as well as the structural stability of the arsenic defects have also been investigated.