Measurements of HO2 chemical kinetics with a new detection method

Research for the period from December 1, 1985 to May 31, 1986 is discussed, i.e., the reaction rate constant of HO2+O3 has been measured with a discharge-flow-tube apparatus. The HO2 radical was detected by the OH(A-X) photofragment emission produced from photodissociative excitation of HO2 at 147 nm. In the meantime, the optical emissions produced by the vacuum ultraviolet excitation of chemical species in the flow tube were investigated and used to examine the possibility for their interference with the HO2 detection. The research results are summarized below

Microscopic picture of aging in SiO2

We investigate the aging dynamics of amorphous SiO2 via molecular dynamics simulations of a quench from a high temperature T_i to a lower temperature T_f. We obtain a microscopic picture of aging dynamics by analyzing single particle trajectories, identifying jump events when a particle escapes the cage formed by its neighbors, and by determining how these jumps depend on the waiting time t_w, the time elapsed since the temperature quench to T_f. We find that the only t_w-dependent microscopic quantity is the number of jumping particles per unit time, which decreases with age. Similar to previous studies for fragile glass formers, we show here for the strong glass former SiO2 that neither the distribution of jump lengths nor the distribution of times spent in the cage are t_w-dependent. We conclude that the microscopic aging dynamics is surprisingly similar for fragile and strong glass formers.Comment: 4 pages, 7 figure

The vibrational predissociation spectroscopy of hydrogen cluster ions

The first infrared spectra of protonated hydrogen clusters in the gas phase have been observed. Predissociation spectra were taken with a tandem mass spectrometer: mass selected hydrogen cluster ions were irradiated inside a rf ion trap by a tunable infrared laser, and the fragment ions created by photodissociation of the clusters were mass selected and detected. Spectra for each product channel were measured by counting fragment ions as a function of laser frequency. Low resolution spectra (Deltanu=10 cm^−1) in the region from 3800 to 4200 cm^−1 were observed for the ions H + 5, H + 7, and H + 9 at 3910, 3980, and 4020 cm−1, respectively. A band was also observed for H + 5 at 3532 cm^−1. No rotational structure was resolved. The frequencies of the band maxima agree well with the frequencies predicted by previous ab initio calculations for the highest modes

Evolution of quantum systems with a scaling type of time-dependent Hamiltonians

We introduce a new class of quantum models with time-dependent Hamiltonians of a special scaling form. By using a couple of time-dependent unitary transformations, the time evolution of these models is expressed in terms of related systems with time-independent Hamiltonians. The mapping of dynamics can be performed in any dimension, for an arbitrary number of interacting particles and for any type of the scaling interaction potential. The exact solvability of a "dual" time-independent Hamiltonian automatically means the exact solvability of the original problem with model time-dependence.Comment: 9 page

Pressure inequalities for nuclear and neutron matter

We prove several inequalities using lowest-order effective field theory for nucleons which give an upper bound on the pressure of asymmetric nuclear matter and neutron matter. We prove two types of inequalities, one based on convexity and another derived from shifting an auxiliary field.Comment: 16 pages, published journal version - includes inequalities for spin polarized system

Theoretical frameworks for testing relativistic gravity. 5: Post-Newtonian limit of Rosen's theory

The post-Newtonian limit of Rosen's theory of gravity is evaluated and is shown to be identical to that of general relativity, except for the PPN parameter alpha sub 2, which is related to the difference in propagation speeds for gravitational and electromagnetic waves. Both the value of alpha sub 2 and the value of the Newtonian gravitational constant depend on the present cosmological structure of the Universe. If the cosmological structure has a specific but presumably special form, the Newtonian gravitational constant assumes its current value, alpha sub 2 is zero, the post-Newtonian limit of Rosen's theory is identical to that of general relativity--and standard solar system experiments cannot distinguish between the two theories

Censusing manatees: a report on the feasibility of using aerial surveys and mark and recapture techniques to conduct a population survey of the West Indian Manatee

This report results from an invitation to review the needs and prospects for capture-recapture and aerial census studies of the manatee (Trichechus manatus) in Florida. Three aerial reconnaissance flights provided a first hand view of manatee habitats, as follows: May 3, Suwannee River to Kings Bay and Crystal River (Rathbun, Eberhardt), May 4, Vero Beach to Ft. Lauderdale and Ft. Myers by way of Whitewater Bay (Rose, Percival, Eberhardt), and May 5, Cape Canaveral to Jacksonville, St. Johns River and Blue Spring (Rose, Kinnaird, Eberhardt). (24 page document

Damped Population Oscillation in a Spontaneously Decaying Two-Level Atom Coupled to a Monochromatic Field

We investigate the time evolution of atomic population in a two-level atom driven by a monochromatic radiation field, taking spontaneous emission into account. The Rabi oscillation exhibits amplitude damping in time caused by spontaneous emission. We show that the semiclassical master equation leads in general to an overestimation of the damping rate and that a correct quantitative description of the damped Rabi oscillation can thus be obtained only with a full quantum mechanical theory.Comment: 5 pages, 5 figure

Evidence for an incommensurate magnetic resonance in La(2-x)Sr(x)CuO(4)

We study the effect of a magnetic field (applied along the c-axis) on the low-energy, incommensurate magnetic fluctuations in superconducting La(1.82)Sr(0.18)CuO(4). The incommensurate peaks at 9 meV, which in zero-field were previously shown to sharpen in q on cooling below T_c [T. E. Mason et al., Phys. Rev. Lett. 77, 1604 (1996)], are found to broaden in q when a field of 10 T is applied. The applied field also causes scattered intensity to shift into the spin gap. We point out that the response at 9 meV, though occurring at incommensurate wave vectors, is comparable to the commensurate magnetic resonance observed at higher energies in other cuprate superconductors.Comment: 8 pages, including 4 figure