[en] It has been suggested that NaH may be detectable in diffuse interstellar clouds. We discuss the photodissociation process of NaH and calculate the rate of destruction by the interstellar radiation field. In the unshielded field, the mean lifetime is about 10 years. There appears to be no efficient gas-phase mechanism for the production of NaH. If it is produced with high efficiency on grain surfaces, abundances of order 10¹⁰ cm^-2 can be achieved. For LiH, a similar analysis leads to an upper limit of 10⁶ cm^-2

[en] Three new excited states of CH⁺ which can be reached by a dipole transition from the ground state with photon energies less than 13.6 eV have been obtained from accurate theoretical calculations. As these states are unbound with respect to nuclear motion, photon absorption into them results in dissociation of the molecule. Photodissociation cross sections have been calculated, and the CH⁺ photodissociation rates in the interstellar radiation field as a function of optical depth have been determined. The rates are approximately 500 times larger than previously assumed. These new photodissociation rates are compared with the rates of other CH⁺ destruction mechanisms in three different models of the interstellar medium. Photodissociation appears to be a significant destruction mechanism in any model requiring large interstellar radiation fields. (Auth.)

[en] The absorption of photons with an energy of 26.9 eV by H₂ produces H⁺ ions with kinetic energies ranging up to 4.4 eV. We attribute the energetic H⁺ ions to absorption into a ¹Σ/sub u/⁺ resonance state of H₂ which autoionizes into a continuum corresponding to a free electron moving in the field of the 1ssigma/sub g/ core of H₂⁺. We present calculations of the real and imaginary parts of the complex potential energy surface of the resonance state and of the transition dipole moment between the ground state of H₂ and the resonance state. The resulting cross section for the production of energetic H⁺ ions and the calculated ratio of H⁺ to H₂⁺ ions produced are in agreement with measurements. The energy distribution of the H⁺ ions has a maximum at about 3.2 eV. The maximum cannot be reproduced by a classical description of the nuclear motion in the autoionizing resonance state, but it does arise when a quantal treatment is used, in which the nuclear motion is governed by the real part of the complex potential

[en] Ab initio CI adiabatic potentials and dipole moment matrix elements for the triatomic dication NH₂²⁺ in the collinear, asymmetric arrangement have been calculated. A diabatic description of the collision process is obtained by a unitary transformation in a representation that diagonalizes the dipole moment matrix. Neglecting H₂ orientation and rotation, cross sections for the charge transfer process N²⁺ + H₂(v=0) → N⁺ + H₂⁺(v') are determined with a close-coupled quantal method. Results will be compared to recent measurements

[en] Calculations are carried out, at similar levels of approximation, of the photoinization cross-sections for the ground X³Σ^-sub(g) and metastable a¹Δsub(g) states of O₂ leading to the X²PIsub(g) state of O⁺₂. Estimates, based upon measurements for the X³Σ^-sub(g) state, are made of the photoionization cross-section of the a¹Δsub(g) state for transitons populating excited states of O⁺₂. (orig.)

[en] A quantal resonance formalism is applied to the calculation of the cross sections for the absorption of photons of energies 26.9 and 30.5 eV into a ¹Σ⁺/sub u/ resonance Rydberg state of H₂. The ¹Σ⁺/sub u/ state undergoes autoionization into the vibrational continuum of the ²Σ⁺/sub g/ state of H⁺₂, producing energetic H⁺ ions. The calculations reproduce state of H⁺₂, producing energetic H⁺ ions. The calculations reproduce the maxima in the measured cross sections at H⁺ energies near 3.2 eV for overestimate the cross sections below 2.5 eV. An arbitrary reduction in the autoionizing widths by a factor of 2 restores agreement over the measured energy range, though more elaborate calculations of the widths suggest that values should be increased

[en] The interaction potentials of the quasimolecular Σ and Pi states formed by the approach of a proton and the positive ion Fe¹³⁺ are calculated in an approximation which reproduces the long-range quadrupole and polarization terms and which accounts properly for short-range penetration effects. The interaction potentials are used in quantal calculations of the cross sections for proton-impact excitation of fine-structure transitions of Fe¹³⁺. Solutions of the close-coupled scattering equations are obtained and the resulting cross sections are compared with those given by the Coulomb-Born and elastic approximations. The sensitivity of the cross sections to features of the interaction potentials is explored. The Coulomb-Born and elastic approximations do not always reflect faithfully the physical characteristics of the potentials

[en] In response to the Comment written by Zhang et al. [Phys. Rev. A 82, 036701 (2010)] we show that the main ideas and results (about the physics and method) reported in our paper [Phys. Rev. A 79, 062715 (2009)] still appear to be correct. Although none of the conjectures given in the Comment about the potential problems in our code are correct, there was a small error in our code, so the part of our paper with numerical data, presented to support our method, appears to be incorrect. The wealth of resonance features in the x-ray line 3D demonstrated in our paper still appears to be real and is reconfirmed by a revised calculation with the error fixed.

[en] We demonstrate monolayer (1L) MoS₂ grown by chemical vapor deposition (CVD) with transport properties comparable to those of the best exfoliated 1L devices over a wide range of carrier densities (up to ∼10¹³ cm⁻²) and temperatures (80–500 K). Transfer length measurements decouple the intrinsic material mobility from the contact resistance, at practical carrier densities (>10¹² cm⁻²). We demonstrate the highest current density reported to date (∼270 μ A μ m⁻¹ or 44 MA cm⁻²) at 300 K for an 80 nm long device from CVD-grown 1L MoS₂. Using simulations, we discuss what improvements of 1L MoS₂ are still required to meet technology roadmap requirements for low power and high performance applications. Such results are an important step towards large-area electronics based on 1L semiconductors. (letter)

[en] Theory and experiment are being used together to explore spectra from sodium and xenon gas mixtures similar to those used in high pressure lamps. Results from high precision measurements of the absorption coefficients over the wavelength range from 425 to 760 nm are presented with 0.02 nm spectral resolution. Measurements of the sodium density with ±5 percent uncertainty complement the absorption coefficient measurements. The experimental data are compared to quantum-mechanical spectral calculations that utilize recent cold collision and other data. The spectra are sensitive to the interatomic potentials, especially in the far wings in which molecular features such as vibrational-rotational and satellite structures are exhibited. The particular results for Na-Xe are analyzed in detail