Showing papers in "Canadian Journal of Physics in 2002"

An overview of the Odin atmospheric mission

Abstract: Odin is a 250 kg class satellite built in co-operation between Sweden, Canada, France, and Finland and launched in February 2001. It carries two instruments: a 4-band sub-millimetre radiometer used for both astronomy and atmospheric science and an optical spectrometer and infrared imaging system for purely atmospheric observations. As part of the joint mission Odin will observe the atmospheric limb for 50% of the observation time producing profiles of many species of interest in the middle atmosphere with a vertical resolution of 1-2 km. These species include, among others, ozone, nitrogen dioxide, chlorine monoxide, nitric acid, water vapour, and nitrous oxide. An overview of the mission and the planned measurements is given.

Electron-beam ion-trap spectra of tungsten in the EUV

Abstract: At the Livermore electron-beam ion-trap facility, extreme-ultraviolet spectra of tungsten have been recorded in the wavelength range 40–85 A. The electron-beam energy was varied systematically to i...

A vector radiative-transfer model for the Odin/OSIRIS project

Abstract: A vector radiative-transfer code has been developed that is able to accurately and efficiently calculate radiance and polarization scattered from Earth's limb. A primary application of this code will be towards generating weighting functions, based on calculated limb radiances, for the retrieval of trace gases (O 3 ,N O 2, BrO, OClO, and O4) from the optical spectrograph and infrared imaging system (OSIRIS). OSIRIS is a UV-visible instrument on board the Odin satellite that measures limb-scattered light. This model solves the vector radiative-transfer equation using an iterative technique simultaneously in both plane-parallel and spherical-shell atmospheres. OSIRIS simulated limb radiance and polarization and OSIRIS weighting functions are presented along with a discussion of the numerical solution parameters, model intercomparisons and timings, and necessary model improvements. Overall agreement with other models was found to be very good and model speed is comparable to a fast finite-difference code. A set of OSIRIS reference atmospheres have been compiled for use with radiative-transfer models. Each of the 216 atmospheres (18 latitudes 12 months) include profiles of air, pressure, temperature, ozone, NO 2, BrO, and stratospheric aerosols.

Progress in helium fine-structure calculations and the fine-structure constant

Abstract: The long-term goal of this work is to determine the fine-structure constant α from a comparison between theory and experiment for the fine-structure splittings of the helium 1s2p 3PJ states. All known terms of order α5 a.u. (α7 mc2) arising from the electron–electron interaction, and recoil corrections of order α4 µ / M a.u. are evaluated and added to previous tabulation. The predicted energy splittings are ν0,1 = 29 616.946 42(18) MHz and ν1,2 = 2291.154 62(31) MHz. Although the computational uncertainty is much less than ±1 kHz, there is an unexplained discrepancy between theory and experiment of 19.4(1.4) kHz for ν1,2. PACS Nos.: 31.30Jv, 32.10Fn

Canonical perturbation theory for highly excited dynamics

Abstract: This article proposes an unified presentation of recent results dealing with canonical perturbation theory (also called the contact transformation method in the quantum mechanical context), which shows how the theory is best handled for investigating the highly excited dynamics of small molecules. The following systems are successively addressed: (i) semi-rigid molecules (one electronic surface, one minimum), (ii) floppy molecules (one electronic surface, several minima), and (iii) non-Born–Oppenheimer dynamics (several interacting electronic surfaces). The perturbative Hamiltonians obtained from the proposed procedures are checked against exact calculations performed on ab initio surfaces (HCP and HCN) and model Hamiltonians. PACS No.: 31.15Md

The basis problem in many-worlds theories

Abstract: To fully appreciate the significance of the basis problem mentioned by Zurek, and of the impact of quantum decoherence on fundamental issues, one needs to understand certain subtle aspects of the connection between classical and quantum mechanics. This chapter, which is more technical than the others, explains these aspects, and, with the aid of some pictures, their relevance to the basis and decoherence problems.

The SU(2) realization for the Morse potential and its coherent states

Abstract: A realization of the raising and lowering operators for the Morse potential is presented. We show that these operators satisfy the commutation relations for the SU(2) group. Closed analytical expre...

Precise atomic lifetime measurements with stored ion beams and ion traps

Abstract: For many years, atomic lifetime measurements on multiply-charged ions have been done almost exclusively by beam-foil spectroscopy. For low ion charges, however, spin-changing "intercombination" transitions have a rate that renders them too slow for traditional fast-beam techniques. Here ion traps and fast-ion beams have been combined in the concept of heavy-ion storage rings. These devices have permitted not only an extension of intercombination lifetime measurements down to singly charged ions, but they also facilitated similar measurements on electric-dipole forbidden transitions. The electron-beam ion trap (EBIT) complements the storage-ring work for work on highly charged ions. Achievements, technical issues, and prospects are outlined. PACS Nos.: 32.70Cs, 32.30Jc, 34.50Fa

Electrical conductivity and thermo-electric power of a-Se80xInx and Se80xGe20Inx thin films

Abstract: The dc conductivity and thermo-electric power of a-Se80–xInx (x = 5, 10, 15, 20, 30) and a-Se80–xGe20Inx (x = 0, 5, 10, 15, 20) thin films are reported in the present work. The free-charge-carrier ...

Nonresonant effects in one- and two-photon transitions

Abstract: We investigate nonresonant contributions to resonant Rayleigh-scattering cross sections of atoms. The problematic nonresonant contributions set a limit to the accuracy to which atomic spectra deter...

The rotating-saddle trap: a mechanical analogy to RF-electric-quadrupole ion trapping?

Abstract: The rotating-saddle potential ball-bearing trap has long been used as a mechanical analogue to explain the operating principles of the Paul-type RF-electric-quadrupole ion trap. This paper outlines the shortcomings of this analogy, as well as explaining how and why this system remains an excellent tool for explaining ion-trap operation. The basic theory of the operating principles of the rotating-saddle trap is provided, which, unlike the Paul Trap is analytically solvable in the friction-free regime. In addition, some extensions to this theory are presented to examine such effects as friction. These results are compared with the equivalent results for Paul-Trap theory, as well as to experimental results measured with a rotating-saddle trap constructed at the University of Calgary. The technical details of this trap, an excellent tool for either lecture demonstrations or teaching laboratory experiments, are also presented, as well as some comments on building such a trap. PACS Nos.: 45.50-j, 01.50Pa, 32.80Pj

Studies for the Odin sub-millimetre radiometer. II. Retrieval methodology

Abstract: This paper presents the first algorithm developed to retrieve atmospheric vertical profiles of trace gases from calibrated spectra measured by the sub-millimetre radiometer (SMR) onboard the Odin satellite. An estimation of atmospheric profiles is obtained by means of an inversion of the spectra using the Optimal Estimation Method. Great attention is paid to the study of the simultaneous retrieval of several species and nonlinearity effects. The measurement response is defined to give the altitude domain of a good retrieval. Main sources of measurement and forward model errors are characterized and separated into two categories: the fixed errors and the variable errors. We define a standard retrieval strategy that can be applied to theoretically investigate any frequency band of any observing Odin mode. For each frequency band, two categories of species are defined: the target species, i.e., the main species to be retrieved, and the interfering species, i.e., molecules emitting an interfering radiance in the observed band. The standard code is based upon an inversion of spectra using a linearized forward model and simultaneously estimates target species and interfering species. As an example, inversions of synthetic noise-free spectra of ozone and chlorine monoxide within an autocorrelator band ranging from 501.18 to 501.58 GHz are shown to behave as expected in the middle stratosphere and in the lower mesosphere. The error analysis shows retrieval limitations in the lower stratosphere that are mainly induced by the high sensitivity of the retrieval to parameters such as tangent height, accuracy in the vertical profile of the interfering species, and spectral parameters of both target lines and interfering lines.

Visible spectrum of highly charged ions: The forbidden optical lines of Kr, Xe, and Ba ions in the Ar I to Kr I isoelectronic sequence

Abstract: We present experimental data on visible transitions in highly charged ions observed in the Lawrence Livermore National Laboratory (LLNL) electron beam ion traps, including results from lines within...

QED effective action revisited

Abstract: The derivation of a convergent series representation for the quantum electrodynamic effective action obtained by two of us (S.R.V. and D.R.L.) in [Can. J. Phys. 71, 389 (1993)] is reexamined. We pr...

The physics of putting

Abstract: The motion of a rolling golf ball on a sloped golf green is modeled. The resulting calculated path of a golf ball is then used, along with a model of the capture of the golf ball by the hole, to de...

Laser-frequency stabilization using a lock-in amplifier

Abstract: We describe how a lock-in amplifier can be used in a feedback loop to lock the frequency of a laser to an atomic transition in 85Rb. A simple physical explanation is presented to describe the shape...

Studies for the Odin sub-millimetre radiometer: III. Performance simulations

Abstract: Odin is a small, low-cost satellite with a combined astronomical and aeronomical mission. The mission is divided on an equal basis between astronomy and aeronomy. The aeronomy objectives can be divided into four main subjects: stratospheric ozone chemistry, mesospheric ozone chemistry, the summer mesopause region, and the coupling between atmospheric regions. The primary instrument on Odin is the millimetre and sub-millimetre radiometer (SMR), which is used both for astronomy and aeronomy. It is the first satellite to use sub-millimetre frequencies for limb-sounding mode. Odin is also equipped with an optical spectrometer (OSIRIS). This paper is the third of a three-part series and describes the choices of observing modes and the expected performance of the SMR instrument for the aeronomy mission. The relevant frequencies are identified and the exact selection of lines is made. This is followed by a detailed simulation study to determine the achievable altitude coverage together with the corresponding ver...

Studies for the Odin sub-millimetre radiometer: I. Radiative transfer and instrument simulation

Abstract: The Odin satellite mission will include radiometric measurements of the Earth's atmosphere in a limb-sounding mode, using frequencies between 480 and 580 GHz, with the overall aim of retrieving vertical distributions of atmospheric constituents. The current paper, being one of a three-part series, addresses primarily the modelling of atmospheric radiative transfer and the effect of instrumental properties: the forward model. Such a model is required for the retrieval process and this presentation puts emphasis on refraction, sensor characteristics, systematic model errors, and some implementation aspects. Refraction must be considered below about 15 km and an efficient algorithm to include this effect is presented. Sensor parts treated are the antenna, the side-band filter, and the spectrometer. The forward model is also essential for determining the needed weighting functions. A semi-analytical expression for species-abundance weighting functions is derived. To form a common basis for the article series,...

Curling rock dynamics: Towards a realistic model

Abstract: We present a model of curling rock motion, which yields realistic dependence upon the dynamical parameters. The underlying assumptions are motivated by physical arguments. We make clear which of th...

Retrieval of vertical concentration profiles from OSIRIS UV-visible limb spectra

Abstract: The OSIRIS instrument, launched on the Odin satellite in February 2001, includes an optical spectrograph that will record UV–visible spectra of sunlight scattered from the limb over a range of tangent heights. These spectra will be used to retrieve vertical profiles of ozone, NO2, OClO, BrO, NO3, O2, and aerosols, for the investigation of both stratospheric and mesospheric processes, particularly those related to ozone chemistry. In this work, the retrieval of vertical profiles of trace-gas concentrations from OSIRIS limb-radiance spectra is described. A forward model has been developed to simulate these spectra, and it consists of a single-scattering radiative-transfer model with partial spherical geometry, trace-gas absorption, Mie scattering by stratospheric aerosols, a Lambertian surface contribution, and OSIRIS instrument response and noise. Number-density profiles have been retrieved by using optimal estimation (OE) to combine an a priori profile with the information from sets of synthetic ``measure...

Dielectronic recombination-rate coefficients to excited states of Be-like oxygen and dielectronic satellite lines

Abstract: We calculate energy levels, radiative transition probabilities, and autoionization rates for Be-like oxygen (O4+) including 1s2 2lnl' (n = 2–8, l n – 1) and 1s23l' nl (n = 3–6, l n – 1) states by the multiconfigurational Hartree–Fock method (Cowan code) and the perturbation theory Z-expansion method (MZ code). The state selective dielectronic recombination-rate coefficients to excited states of Be-like oxygen are obtained, which are useful for modeling O V spectral lines in a recombining plasma. Configuration mixing plays an important role for the principal quantum number, n, distribution of the dielectronic recombination-rate coefficients for 2snl (n 5) levels at low electron temperature. The orbital angular momentum quantum number, l, distribution of the rate coefficients shows a peak at l = 4. The total dielectronic recombination-rate coefficient is derived as a function of electron temperature. The dielectronic satellite lines are also obtained. PACS Nos.: 34.80Lx, 32.80Dz, 32.30Jc, 31.10+z

MHD free convection flow of a micropolar fluid past a vertical porous plate

Abstract: The present work is concerned with the unsteady flow of an incompressible, viscous, conducting micropolar fluid, through a porous medium, over an infinite plate that is started into motion in its own plane by an impulse. A uniform magnetic field acts in a direction perpendicular to the plate. The governing equations are solved using a state space approach and the inversion of the Laplace transform is carried out, using a numerical approach. The technique is applied to a heated-plate problem and to a problem pertaining to a plate under uniform heating. Numerical results concerning temperature (for both problems), velocity, and microrotation are given and are illustrated graphically. PACS Nos.: 47.00, 65.00, 47.50, 76.00

Quantum mechanics of the damped harmonic oscillator

Abstract: We quantize the system of a damped harmonic oscillator coupled to its time- reversed image, known as Bateman's dual system. By using the Feynman-Hibbs method, the time-dependent quantum states of such a system are constructed entirely in the framework of the classical theory. The geometric phase is calculated and found to be proportional to the ground-state energy of the one-dimensional linear harmonic oscillator to which the two-dimensional system reduces under appropriate constraint.

The run of a golf ball

Abstract: The run, which includes both the bounce and the roll, of a golf ball landing on turf is modeled. The effect of launch speed, impact angle, backspin, and green firmness on the run for a variety of golf shots is considered. It is found that the dominant factor that determines the length of the run, in the case of drives, is the impact angle. It is also found that for high-lofted iron shots, where the golf ball is given sufficient backspin, the ball may, for firm enough greens, initially bounce forward before running backwards. PACS No.: 01.80+b

The structure of light nuclei and its effect on precise atomic measurements

Abstract: The paper consists of three parts: (i) what every atomic physicist needs to know about the physics of light nuclei (and no more); (ii) what nuclear physicists can do for atomic physics; and (iii) what atomic physicists can do for nuclear physics. A brief qualitative overview of the nuclear force and calculational techniques for light nuclei will be presented, with an emphasis on debunking myths and on recent progress in the field. Nuclear quantities that affect precise atomic measurements will be discussed, together with their current theoretical and experimental status. The final topic will be a discussion of those atomic measurements that would be useful to nuclear physics. PACS No.: 31.30Gs

Measurement of radiative lifetimes in Pr II and Nd II

Abstract: We have measured the radiative lifetimes of 33 levels of Pr II and 13 levels of Nd II using two variants of the beam-laser method. The levels studied had term energies up to ∼30 000 cm −1 and lifetimes in the range 6-170 ns. Experimental accuracy was in the range 1-11% . We have used these lifetimes to update transition probabilities for 82 transitions in Pr II in the wavelength range 392-640 nm, which are useful for stellar abundance determinations.

Radiation effect on MHD free-convective flow of a gas past a semi-infinite vertical plate with variable thermophysical properties for high-temperature differences

Abstract: Radiation effects in the presence of a uniform transverse magnetic field on the free-convective steady laminar boundary-layer flow, past a semi-infinite vertical plate, for high-temperature differe...

The impact of the OSIRIS grating efficiency on radiance and trace-gas retrievals

Abstract: The optical spectrograph and infrared imaging system (OSIRIS), launched in 2001, is a UV–visible diffraction-grating instrument designed to measure light scattered from the Earth's limb. Laboratory measurements of the OSIRIS diffraction-grating efficiency reveal a sensitivity to polarization including an anomalous structure of width 20–30 nm introduced into light polarized in a direction perpendicular to the grooves of the grating. A vector radiative-transfer model was used to generate synthetic OSIRIS spectra in an effort to examine the effect of this on radiances and trace-gas retrievals. Radiances that included grating effects were found to deviate by nearly 10% from those that did not and also contained the anomalous structure. Performing differential optical absorption spectroscopy (DOAS) on these spectra revealed errors in ozone apparent column densities of up to 80 DU. The size of the error was controlled mainly by the difference in polarization between the two DOAS spectra. Two possible correction...

Potential curves and rovibrational energies for electronic states of the molecular ion KCs

Abstract: The KCs+ molecular ion potential curves are investigated over a wide range of internuclear distance for electronic states described in a 2Λ(+) representation (neglecting the spin-orbit effect) as well as in an Ω(+) representation (including the spin-orbit effect). This calculation has been done in a one active electron approach by using an ab initio method based on non-empirical pseudopotentials with core-valence effect taken into account through parameterized l-dependent polarization potentials. Gaussian basis sets have been used for both atoms, and spin-orbit effects have been taken into account through a semiempirical spin-orbit pseudopotential. The canonical functions approach is used to do a rovibrational study by calculating the eigenvalues Ev, the rotational constant Bv, the centrifugal distortion constants Dv (up to 106 vibrational levels), and the spectroscopic constants are deduced for six bound states. The permanent and transition dipole moment functions have been derived for transitions betwee...

The g factor in a light two-body atomic system: a determination of fundamental constants to test QED

Abstract: The energy levels of a two-body atomic system in an external homogeneous magnetic field can be presented in terms of the magnetic moments of their components, however, those magnetic moments being ...