Aerosol size spectra from spectral extinction data: the use of a linear inversion method

Classified abstracts 5502-5512 33 5502. Positron-g8s QogEgcctiw mea smements. (Canada) The purpose of this paper is to review the progress in positron-gas crosssection Total cross-section measurements for measurements. 0.3-1000 eV e+-He, NC, Ar, RI, Xc, Hz, N,, CO,, Oz. CH* and CO are summarized. Interesting shape features in the total cross-section curves, such as Ramsauer-Townsend effects and the onsets of positronium formation are discussed. An effort is made to compare total cross-section measurements from different laboratories to see if there are any consistencies which could provide information on the reliability of the various measurements. Comparisons of total cross-section measurements for positrons and electrons colliding with several of the above gases are presented in an attempt to illustrate the similarities and differences between positron and electron scattering. Some recent positron crosssection investigations pertaining to differential scattering positronium formation, inelastic scattering, atomic excitation and resonance searches are also discussed. (USA) W E Kauppila ml T S Stein, Can J Phys, 60 (4), 1985471493. 33 5503. The interaction of positrom 8nd positronium with sm8U 8toms. (Canada) This is a report on recent progress in the theory of small atomic systems in&ding a positron. I have selected four main topics that seem interesting, instead of trying to cover the entire extensive subject. First, I consider the two-channel region in e+-H scattering which lies between 6.8 and 10.2 eV, and have reported the results of positronium-formation and resonantscattering calculations. Second, I introduce the concept of ‘iso-leptonic families’with fixed electron and positron numbers and discuss in detail the two-electron, one-positron family. This family includes several interesting bound and resonant states. Next, I derive a new method of calculating positron annihilation rates and cross-sections from approximate wave functions. Although more difficult to apply than the direct method, this technique is more accurate. Finally, I show the applicability of many positron calculations to currently interesting astrophysical problems, especially the recent observations of annihilation radiation coming from the direction of the galactic ctntre. (USA) Rickard J Drackman, Gun J Phys, 60 (4). 1985494-502. 33 5504. The difference between the electron temperature 8nd tbe gas teqefIItUre i0 8 &Wi0118~ 8rc PhSrrm 8t 8tmospberic presure. (GB) This paper deals with an experimental and theoretical study of the difference between the electron temperature T, and the gas temperature T, in a stationary cylindrical argon plasma. The experimental method is based on the measurement of a line coefficient, during the first microseconds of plasma decay, which presents a jump due to the equalization of temperatures. A theoretical model with rate equations and the electron energy balance has been developed. The comparison between experimental and theoretical values of the difference (T,-T,.has been carried out for several current intensities and radial pontoons. The agreement is good for an arc with a 6 mm diameter. For a 4 mm diameter the computed values are less precise than the experimental ones because of the inaccuracy of diffusion terms which play an important part in the computation of (T,-T,). (France) A Gieizes et al, J Phys D: Appl Phys, 15 (6). 1982, 1031-1045. 33 5505. Plasma composition in 8 ps-lines pinch. (GB) The properties of a new spectroscopic light source are analysed. It is demonstrated that the gas-liner pinch emits resonance lines from a homogeneous central layer without self-absorption effects. For investigations of the Lyman-a line, the electron density is adjusted to N,-2 x lO’* cm-” and the electron temperature to kT,-7 eV. (West Germany) K H Finken and U Ackermann, J Phys D: Appl Phys, 15 (4), 1982,615-620. 33 5506. Selfcoasistent akolatioa of tke hydrogen phma parameters: I. Stationary phsmar (GB) Hydrogen plasma parameters have been calculated for a glow discharge driven by 0.1 A current in a 0.4 cm tube at 270 Pa and 530 Pa initial gas pressures. The set of differential equations that includes levels population, electron density and electron temperature rate equations has been solved simultaneously and the stationary plasma parameters have been evaluate-d. (Yugoslavia) N N Ljepojevibet Pi, J Phys D: Appl Phys, 15 (4), 1982, 621629.

33 5507. Large rrossecctioa pulsed TEA-CO, interferometer for plasma d&nosh (USA) A large cross-section Mach-Zchnder interferometer is illuminated by a 30 ns CO, laser pulse. The line-integrated density sensitivity- is 2 x 1019m-‘. Spatial features down to 150 rrm can bc identified within a usable field of vi&v of 50 mm. An example oia typical interference pattern obtained on a plasma column is shown together with its corresponding Abel deconvoluted density profile. J L Lackuhe et al, Appl Optics, 21 (14). 1982,2538-2540. 34. ELECTRONICS TECHNOLOGY

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34 5508. Freqoency m of 8 tberm8iiy driven 8tmospke. (USA) A focus dithered CO, beam has been used to thermally dither the atmosphere in a laboratory thermal blooming cell. The amplitude and phase response of the dithered atmosphere were measured using both an He-Ne laser and a CO1 laser. If a relaxation time determined by the beam diameter and the crosswind velocity is introduced, the atmospheric response can be described analytically by using the theory for the propagation of acoustic waves in an absorptive and dispersive fluid. Julian S NiiIas 8Ild Den& C Doneman, Appl Optic, 21 (3), 1982, 421-427. 34 5509. Atmospheric premnre monitoring of trace &rscsming tunable diode lasers (USA) High-sensitivity measurements of infrared absorptions due to isolated lines broadened by air at atmospheric pressure are reported. Tunable diode lasers and harmonic techniques were employed to detect absorptions as small as 0.01 y0 over path lengths up to 250 m through the open air. The limiting noise source is caused by a base line signal which varies with the optical alignment. The reported sensitivity is not a fundamental limit. Techniques for further increasing sensitivity are discussed. (Canada) D T C8tidy and J Reid, Appl Optics, 21 (7). 1982, 1185-1190. 34 5510. Aerosol size spectra from spectmi eXthcth d8t8: the me of 8 hear inversion metbod. (USA) A modification of the Twomey-Phillips linear constrained inversion method is used to retrieve aerosol size spectra from simulated spectral optical depths in the wavelength range from 0.37 to 2.2 pm. It is found that the transition between nonphysical solutions to well-behaved ones, which is driven by the smoothing parameter y, is gradual and that negative components, when present in the solution, always belong to the smallest particle range. When values of y great& than 0.05 are required to obtain well-behaved solutions, a strong bias on the retrieved solution is posed by the form of the first-guess solution. Moreover, even if the retrieved size distribution computed for low values of y is not well-behaved, much information on the shape of the true solution in the medium and large particle range is contained in the retrieved solution. The effect of realistic random errors added to the simulated optical depths is also discussed. (Italy) R Rii et al, Appl Optics, 21 (9), 1982, 1578-1587. 34 5511. Magnetic dipole infrared atmospberii oxygen bands. (USA) Molecular vibration and rotation constants are obtained for the metastable a’b, electronic state of molecular oxygen. The constants are given for the u =0 and u = 1 vibrational levels by combining recent highresolution laboratory measurements with high-resolution observatorybased planetary and solar spectra of the magnetic dipole transitions of the system o’A,+-X%;. Laurence S Rothman, Appl Optics, 21 (13). 1982, 2428-2431. 34 5512. Validation of tbe BUV satellite ozone sensor osing the rocket ozonesonde. (USA) This paper reviews aspects of the rocket ozonesonde (ROCOZ) performance pertaining to the validation of satellite ozone sensing systems, particularly the backscattered ultraviolet (BUV) sensor. It is shown that while the BUV system relates cumulative vertical ozone to pressure, the ROCOZ can measure cumulative ozone as a function of radar altitude. As a consequence some method of relating atmospheric pressure and altitude is required, with a concomitant error introduced. A Monte Carlo simulation was performed to evaluate the contribution of scattered flux on the ROCOZ result. The scattered component always causes an underesti351