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A large survey of galaxies in the CO (J=1-0) line is presented. Among different types of active galaxies, within the sample, the detection rate is found to be: Starbursts (15 percent), Liners (60 percent), Seyferts (30 percent). A look at the subsample that is located within 40 Mpc (Ho = 75 km s(-1) Mpc(-1) regarding local density of galaxies reveals no substantial difference between detections and non-detections.
The potential advantages of laser diode pumped solid state lasers are many with high overall efficiency being the most important. In order to realize these advantages, the solid state laser material needs to be optimized for diode laser pumping and for the particular application. In the case of the Nd laser, materials with a longer upper level radiative lifetime are desirable. This is because the laser diode is fundamentally a cw source, and to obtain high energy storage, a long integration time is necessary. Fluoride crystals are investigated as host materials for the Nd laser and also for IR laser transitions in other rare earths, such as the 2 micron Ho laser and the 3 micron Er laser. The approach is to investigate both known crystals, such as BaY2F8, as well as new crystals such as NaYF8. Emphasis is on the growth and spectroscopy of BaY2F8. These two efforts are parallel efforts. The growth effort is aimed at establishing conditions for obtaining large, high quality boules for laser samples. This requires numerous experimental growth runs; however, from these runs, samples suitable for spectroscopy become available.
Water vapor is an important minor constituent in the studies of the middle atmosphere for a variety of reasons, including its role as a source for active HO(y) chemicals and its use in analysis of transport processes. A number of in situ and remote techniques were employed in the determination of water vapor distributions. Two of the more complete data sets were used to develop an interim reference profile. First, there are the seven months of Nimbus 7 limb infrared monitor of the stratosphere (LIMS) data obtained during Nov. 1978 to May 1979 over the range 64S to 84N latitude and from about 100 to 1 mb in the mid-mesosphere at several fixed Northern Hemisphere mid-latitude sites. These two data sets were combined to give a mid-lattitude, interim reference water vapor profile for the entire vertical range of the middle atmosphere and with accuracies of better than 25 percent. The daily variability of stratospheric water vapor profiles about the monthly mean was also established from these data sets for selected months. Information is also provided on the longitudinal variability of LIMS water vapor profiles about the daily, weekly, and monthly zonal means. Generally, the interim reference water vapor profile and its variability are consistent with prevailing ideas about chemistry and transport.
A single-stage, frequency-doubled, copper vapor laser-pumped dye laser has been constructed to be used in the measurement of atmospheric hydroxyl radical concentrations. A new photon counting instrument is used for HO fluorescence detection. Theoretical and experimental studies of instrument performance show better sensitivities and reduced photolytic interferences than have been possible with previous systems based upon Nd:YAG pumping.
The reaction of the hydroxyl radical (HO) with the stable carbon isotopes of methane has been studied as a function of temperature from 273 to 353 K. The measued ratio of the rate coefficients for reaction with (C-12)H4 relative to (C-13)H4 (k12/k13) was 1.0054 (+ or - 0.0009 at the 95 percent confidence interval), independent of temperature within the precision of the measurement, over the range studied. The precision of the present value is much improved over that of previous studies, and this result provides important constraints on the current understanding of the cycling of methane through the atmosphere through the use of carbon isotope measurements.
The vertical distributions of the important highly reactive stratospheric species, ClO and HO2, have been inferred from Spacelab 3 (May 1985) Atmospheric Trace Molecule Spectroscopy (ATMOS) measurements of more detectable radical and reservoir species. A simple steady state algebraic expression for ClO, utilizing the observed ClONO2/NO2 abundance ratio, approximates the ClO results of a time-dependent photochemical model at sunset (30 deg N). Balloon measurements of ClO and comparisons of time-dependent photochemical model calculations of ClONO2 and HCl with the corresponding ATMOS profiles suggest that the actual ClO values are less than the time-dependent model profiles for ClO at sunset and sunrise (47 deg S). Errors in the current model simulation of the partitioning among the principal free chlorine species (HCl, ClONO2, and ClO) are indicated. The accuracy of the time-dependent model calculations of HO2 is suggested by the agreement between model results and ATMOS observations for HO2NO2 and balloon measurements of HO2. This confirms for the first time the procedure suggested previously by a number of authors of deriving HO(x) abundances from observed fields of O3 and H2O.
Using electron count rate data at geostationary orbit, daily energy spectra, extending from 30 keV to 15 MeV, have been developed for trapped relativistic electrons at 6.6 earth radii. These spectra have been used to model the flux of these electrons into the atmosphere at 120 km. Energy deposition calculations permit daily sources of HO(x) and NO(y) to be calculated at auroral and subauroral latitudes due to relativistic electron precipitation (REP) for the period June 13, 1979, through June 4, 1988. Both short-term and long-term source variations are quite large over the period considered. The results suggest that a significant contribution to the anomalously large and unexplained global O3 declines between 1979 and 1985 has been made by the catalytic destruction of O3 by odd nitrogen in the lower stratosphere at mid to high latitudes. The results also provide evidence for a clear and strong linkage between solar variability, the state of the magnetosphere, and the chemical climatological state of the middle and lower atmosphere.
As part of the NASA/FAA National Integrated Windshear Program, a measurable windshear hazard index has been defined that can be remotely sensed from an aircraft, to give the pilot information about the wind conditions along the flight path. A technology analysis and end-to-end performance simulation measuring signal-to-noise ratios and resulting wind velocity errors for competing coherent laser radar (lidar) systems have been carried out. The results show that a Ho:YAG lidar at a wavelength of 2.1 microns and a CO2 lidar at 10.6 microns can give the pilot information about the line-of-sight component of a windshear threat from his present position to a region extending 2-4 km in front of the aircraft. This constitutes a warning time of 20-40 s, even in conditions of moderately heavy precipitation.
A narrowband UV Raman scattering system is used to obtain measurement profiles of major and minor species concentrations, temperature, and mixture fraction in opposed jet diffusion flames. The measurement profiles can be compared to previously obtained temperature and concentration profiles (Pellett et al., 1989), obtained using CARS, and they can also be qualitatively compared to the predicted concentration and temperature profiles in pure hydrogen/air flames (Gutheil and Williams, 1990) and in diluted hydrogen/air flames (Dixon-Lewis and Missaghi, 1988; Ho and Isaac, 1991). The applied stress-rates for the two flame conditions studied are 240/s and 340/s, with respective hydrogen concentrations in the fuel jet of 0.67 and 0.83, on a mole fraction basis (0.13 and 0.26 hydrogen mass fractions, respectively).
In order to improve the constraints on models of the mesospheric response to solar UV variations, an analysis is conducted of the Solar Mesosphere Explorer (SME) IR ozone data and Nimbus 7 stratosphere and mesosphere sounder (SAMS) temperature data. Maximum low-altitude ozone and temperature-response amplitudes occur at about the same altitude, where a strong coupling between photochemical and thermal components of the mesospheric response is suggested by the simultaneous positive temperature and negative ozone response maxima. Increased Lyman-alpha dissociation of water vapor and temperature feedback are theorized to account for the negative ozone response. HO(x) chemical heating can increase as ozone destruction increases, and can therefore account for the positive temperature response.
Tropospheric chemical transformations of alternative hydrofluorocarbons (HCF's) and hydrochlorofluorocarbons (HCFC's) are governed by hydroxyl radical initiated oxidation processes, which are likely to be analogous to those known for alkanes and chloroalkanes. A schematic diagram is used to illustrate plausible reaction mechanisms for their atmospheric degradation, where R, R', and R'' denote the F- and/or Cl-substituted alkyl groups derived from HCF's and HCFC's subsequent th the initial H atom abstraction by HO radicals. At present, virtually no kinetic data exist for the majority of these reactions, particularly for those involving RO. Potential degradation intermediates and final products include a large variety of fluorine- and/or chlorine-containing carbonyls, acids, peroxy acids, alcohols, hydrogen peroxides, nitrates and peroxy nitrates, as summarized in the attached table. Probably atmospheric lifetimes of these compounds were also estimated. For some carbonyl and nitrate products shown in this table, there seem to be no significant gas-phase removal mechanisms. Further chemical kinetics and photochemical data are needed to quantitatively assess the atmospheric fate of HCF's and HCFC's, and of the degradation products postulated in this report.
Ultra-Sensitive Coherent Detection (USCT) and conventional heterodyne detection methods were evaluated for use as a space-borne wind sensing system. For this study, we assume that the wind sensing system would be available by the year 2015. Consequently, laser systems and detectors more advanced than those under consideration for near term programs could be included. Three laser candidates under evaluation are Nd-YAG at 1.06 microns, Ho-YAG at 2.1 microns, and CO2 at 9.11 microns. Both heterodyne and USCD detection methods were included. The primary stress is on the optimization of weight and power consumption of the wind sensor portion of the satellite system.
The increasing interest in the development of an eye-safe, solid state, Doppler lidar for avionic applications has created the need for a quantitative evaluation of atmospheric effects on performance. Theoretical calculations were completed for optical scattering parameters to be compared with the field measurements. Computer codes were developed for the required calculations and designed to be interactive and user friendly in order to support comparison with experimental results and, thus, provide the basis for evaluation of eye-safe Doppler lidar over a wide range of atmospheric conditions and geographical locations. A holmium Doppler lidar operating at 2.09 microns was constructed for atmospheric backscattering, attenuation, and wind velocity measurements. Theoretical calculations and field studies were performed for backscatter coefficients. The selected wavelengths correspond to Er:glass, Tm:YAG, and Tm,Ho:YAG solid state lasers that are suitable for use in an eye-safe Doppler lidar system.
Significant progress has been made in recent years in the development of new, solid-state laser sources. This talk will present an overview of some of the new developments in solid-state lasers, and their application toward lidar/DIAL measurements of the atmosphere. Newly emerging lasers such as Ho:YAG, Tm:YAG, OPO, and Ti:Sapphire will be covered, along with the spectroscopic parameters required for differential operational modes of atmospheric remote sensing including Doppler-Windshear lidar, Tunable laser detection of water/CO2, and broad linewidth OPO's for open path detection of pollutant hydrocarbon gases. Additional considerations of emerging laser technology for lidar/DIAL will also be covered.
Stratospheric concentrations of HO2, H2O2, and OH have been retrieved simultaneously from the far-infrared emission spectra obtained with a balloon-borne Fourier transform spectrometer in June 1983 at 32 deg N latitude. Retrieved concentrations of HO2 and H2O2 are reported, along with vertical distributions of OH which were reported in an earlier paper for the afternoon, sunset, and nighttime periods for altitudes from 26 to 38 km. HO2 distributions are obtained with uncertainties that are about the same as OH for the same vertical range and for the afternoon and sunset periods. H2O2 concentration is obtained at an altitude of 30 km for the period that covers afternoon and sunset hours. The retrieved concentrations of these HO(x) species agree well with other individually measured results and the steady state photochemical predictions. The ratio HO2/OH at around 32 km seems to increase from the afternoon period to the sunset period.
A new proof is given for Jacobi's no-conjugate-point necessary condition. For a certain class of linear-quadratic optimal control problems it is shown that the existence of a conjugate point in the interior of the extremal implies the existence of control perturbations that lead to a reduction in cost. In a well-known way, through the concept of the accessory minimum problem, this results in a no-conjugate-point condition for general optimal control problems. Important ideas used in this work are adopted from Breakwell and Ho (1965). In contrast to earlier results, the new proof also applies if the coefficient functions of time associated with the accessory minimum problem have any finite number of discontinuities.
HO2 concentrations at two Oregon sites were determined for continuous periods of 36 to 48 hours, using fluorescence assay with gas expansion. At the sea level coastal site, NNW winds prevailed during daytime, and a point measurement of very low total nonmethane hydrocarbon concentration indicated the presence of remote tropospheric air of oceanic origin. At the urban site, HO2 was determined during moderately low ozone pollution levels. At both sites, maximum daily (HO2) was in the range of 1-2 x 10 exp 8/cu cm under clear-sky conditions, with an estimated overall uncertainty of 40 percent. HO2 was detected by continuous low-pressure sampling with flowing chemical conversion to HO, which was detected by laser-excited fluorescence. The instrumental response to HO2 was calibrated by the self-decay of HO2 at atmospheric pressure. Interference in the measured daytime HO2 concentrations by RO2 was estimated at less than 20 percent.
Fabry-Perot resonators have been used to demonstrate single-mode lasing of holmium and neodymium YAG. The previous demonstration in the holmium laser required TE cooling the crystal to -15 C in order to achieve threshold. The present study extends that result, demonstrating +25 C operation in a 1-mm thick plano/plano resonator. The experimental configuration of lasing both the holmium and thulium lasers used a 500-mW diode laser which was collimated, circularized, and focused into a beam radius of 60 microns. The single-frequency lasing spectrum of the holmium laser is shown. By adjusting the mirror reflectivity, the ability to control the laser's wavelength is demonstrated. This laser operated with 11 mW of optical power, a 57-percent slope efficiency, and 120-mW threshold vs absorbed diode power laser for the 60-micron beam radius. The thulium laser operated very efficiently at room temperature, but on seven longitudinal modes. The Tm:TAG laser exhibits typical characteristics of spatial hole burning not seen in the Ho:Tm:YAG for flat/flat resonators.