Studies of multichannel rotational predissociation of Ar–H2 van der Waals molecule by the complexcoordinate coupledchannel formalism

This is the published version, also available here: http://dx.doi.org/10.1063/1.442929.The complex‐coordinate coupled‐channel (CCCC) formalism previously developed [J. Chem. Phys. 72, 4772 (1980)] is applied to the accurate determination of the level widths (lifetimes) and energies of rotationally predissociating metastable Ar⋅⋅⋅H2 van der Waals molecules. Calculations are performed using several realistic anisotropic potentials obtained recently by experiments, including Lennard‐Jones (LJ), Buckingham–Corner (BC) type potentials, as well as the semiempirical potential of Tang–Toennies (TT). New numerical methods are introduced here to deal with the complex rotations of piecewise inhomogeneous potentials such as those of BC and TT. It is found that the CCCC method is capable of providing reliable results for any given potential surface. Furthermore, the CCCC results are sensitive to the potential surfaces used. For example, the linewidths predicted for different LJ potential surfaces considered here vary by a factor as large as 4. However, the agreement among more recent potentials, namely, the BC potential of Zandee and Reuss and that of Le Roy and Carley as well as the potential of Tang and Toennies, is much closer: the resonance energies agree to within 1 cm−1 and the linewidths to within 30%

Density-functional calculations on singly and doubly excited Rydberg states of many-electron atoms

This is the published version, also available here: http://dx.doi.org/10.1103/PhysRevA.65.052508.Nearly 100 low-, moderately high-, and high-lying singly and doubly excited states of He, Li, and Be have been calculated using a nonvariational, work-function-based exchange potential within the nonrelativistic Hohenberg-Kohn-Sham density-functional theory (DFT). The nonlinear gradient included in the Lee-Yang-Parr correlation functional is used to incorporate the correlation potential. The generalized pseudospectral method is used for nonuniform and optimal spatial grid discretization and solution of the Kohn-Sham equation to obtain accurate eigenvalues, expectation values, and radial densities for both ground and excited states. The results are compared with the available theoretical and experimental data. The discrepancy in the calculated singly excited state energies is within about 0.01% for He (for other atoms, it is less than 0.2%), while that for the doubly excited states of He is well within 3.6%. The deviations in the calculated single- and double-excitation energies for 31 selected states are in the error ranges 0.009–0.632 % and 0.085–1.600 %, respectively. The overall agreement of the present results is quite gratifying, especially in the light of DFT’s difficulties in dealing with excited states. The exchange-only results are practically of Hartree-Fock quality, and the correlation-included results are usually slightly overestimated. The present method offers a simple, computationally efficient and general scheme for accurate calculation of multiply excited Rydberg states within DFT

Quantum-fluid-dynamics approach for strong-field processes: Application to the study of multiphoton ionization and high-order harmonic generation of He and Ne atoms in intense laser fields

This is the published version, also available here: http://dx.doi.org/10.1103/PhysRevA.65.043402.We explore the feasibility of extending the quantum-fluid dynamics (QFD) approach for quantitative investigation of nonlinear optical processes of many-electron quantum systems in intense laser fields. Through the amalgamation of the QFD and density-functional theory (DFT), a single time-dependent hydrodynamical equation of motion can be derived. This equation has the form of a generalized nonlinear Schrödinger equation (GNLSE) but includes the many-body effects through a local time-dependent exchange-correlation potential. The time-dependent generalized pseudospectral method is extended to the solution of the GNLSE in spherical coordinates, allowing nonuniform spatial discretization and efficient, accurate solution of the hydrodynamical density and wave function in space and time. The procedure is applied to the study of multiphoton ionization (MPI) and high-order harmonic generation (HHG) of He and Ne atoms in intense laser fields. Excellent agreement with other recent self-interaction-free time-dependent DFT calculations is obtained for He, while for Ne, good agreement is achieved. Four different exchange-correlation energy functionals are used in the study with an aim to explore the roles of exchange and correlation on MPI/HHG processes in details. The method offers a conceptually appealing and computationally practical approach for nonperturbative treatment of strong-field processes of many-electron systems beyond the time-dependent Hartree-Fock level

Nevirapine- and efavirenz-associated hepatotoxicity under programmatic conditions in Kenya and Mozambique.

To describe the frequency, risk factors, and clinical signs and symptoms associated with hepatotoxicity (HT) in patients on nevirapine- or efavirenz-based antiretroviral therapy (ART), we conducted a retrospective cohort analysis of patients attending the ART clinic in Kibera, Kenya, from April 2003 to December 2006 and in Mavalane, Mozambique, from December 2002 to March 2007. Data were collected on 5832 HIV-positive individuals who had initiated nevirapine- or efavirenz-based ART. Median baseline CD4+ count was 125 cells/μL (interquartile range [IQR] 55-196). Over a median follow-up time of 426 (IQR 147-693) days, 124 (2.4%) patients developed HT. Forty-one (54.7%) of 75 patients with grade 3 HT compared with 21 (80.8%) of 26 with grade 4 had associated clinical signs or symptoms (P = 0.018). Four (5.7%) of 124 patients with HT died in the first six months compared with 271 (5.3%) of 5159 patients who did not develop HT (P = 0.315). The proportion of patients developing HT was low and HT was not associated with increased mortality. Clinical signs and symptoms identified 50% of grade 3 HT and most cases of grade 4 HT. This suggests that in settings where alanine aminotransferase measurement is not feasible, nevirapine- and efavirenz-based ART may be given safely without laboratory monitoring

Evidence for the Role of Instantons in Hadron Structure from Lattice QCD

Cooling is used as a filter on a set of gluon fields sampling the Wilson action to selectively remove essentially all fluctuations of the gluon field except for the instantons. The close agreement between quenched lattice QCD results with cooled and uncooled configurations for vacuum correlation functions of hadronic currents and for density-density correlation functions in hadronic bound states provides strong evidence for the dominant role of instantons in determining light hadron structure and quark propagation in the QCD vacuum.Comment: 26 pages in REVTeX, plus 10 figures, uuencoded. Submitted to Physical Review D. MIT-CTP-226

The first operation and results of the Chung-Li VHF radar

The Chung-Li Very High Frequency (VHF) radar is used in the dual-mode operations, applying Doppler beam-swinging as well as the spaced-antenna-drift method. The design of the VHF radar is examined. Results of performance tests are discussed

Two‐photon dissociation of vibrationally excited HD+: The inhomogeneous differential equation approach

This is the published version, also available here: http://dx.doi.org/10.1063/1.451229.We extend the inhomogenous‐differential‐equation (IDE) approach of Dalgarno and Lewis for a detailed study of two‐photon dissociation (TPD) of HD+ from high vibrational levels of the 1sσ g electronic state. Contrary to the H+ 2 case, where the TPD cross sections σ(2) L are largest near TPD thresholds and decrease monotonically with increasing photon energy, the HD+ cross sections are characterized by rich resonant and interference structures. We present σ(2) L results for TPD from the initial v i =6, 8, 10, 12, 14, 16, and j i =0 levels as well as from v i =14, j i =0, 2, 4 levels for a wide range of wavelengths of linearly polarized radiation accessible by CO2 and CO lasers. It is found that while there are four TPD pathways, the channel 1sσ g (v i   j i )→ω 1sσ g (v, j=j i ±1) →ω2pσ u (k, j   f =j±1) dominates the two‐photon process in most of the cases we have studied. Further, the results show that σ(2) L increases rather rapidly as the initial vibrational quantum number v i increases, indicating that the hereronuclear diatomic molecules in high vibrational levels can be efficiently two‐photon dissociated by IR lasers. Consequently molecular structures near the dissociation limit may be conveniently probed by two‐photon spectroscopy—as has indeed been demonstrated recently by experiments. Our σ(2) L results thus provide complementary information to the HD+spectroscopic data obtained recently by Carrington e t a l

Responding to Major Burn Disasters in Resource-Limited Settings: Lessons Learned From an Oil Tanker Explosion in Nakuru, Kenya.

BACKGROUN

Quantum dynamics of molecular multiphoton excitation in intense laser and static electric fields: Floquet theory, quasienergy spectra, and application to the HF molecule

This is the published version, also available here: http://dx.doi.org/10.1063/1.444219.The multiphoton excitationdynamics of vibration‐rotation states in diatomic molecules in intense laser and static electric fields is investigated. The Floquet matrix method is used to calculate the quasienergy and multiphoton absorptionspectra of the HF molecule as functions of field strengths and frequency. Nonlinear effects such as power broadening, dynamic Stark shift, Autler–Townes multiplet splitting, hole burning, and S‐hump behaviors, etc., are observed and discussed in terms of quasienergy diagrams. Many of the salient features in the spectral line shapes may be qualitatively understood in terms of an analytical three‐level model. The addition of a dc electric field removes the restriction of the rotational dipole selection rule and causes significant intermixing of the bare molecular vibrator states. Due to the greater number of strongly coupled nearby states in the dc field, nonlinear effects such as those mentioned above appear at a much lower ac field strength than they would in the absence of the dc field. The introduction of an external dc field, therefore, strongly enhances the multiphoton excitation probabilities and results in a much richer spectrum