No abstract

X study has bee11 made of the discrepancy between the X-atom content of active nitrogen as inferred from the maximum IHCN production from the reaction of many hydrocarbons, and that indicated by the extent of NO destruction. The IHCX production from several hydrocarbons was similar a t high reaction temperatures in a spherical reaction vessel, and was independent of reaction t e m p e r a t~~r e in a cylindrical reaction vessel. The ratio (NO destroyed)/ (HCN produced) was found to be independent of the mode of excitation bf the molec~rlar nitrogen ancl of the N-atom concentration, and to be ~~naffectecl by the addition, upstream, of N?O or CO?. Although NH:, was found to be a minor product of the hydrocarbon reactions, HCN accounted for a t least 96% of the N-atom content of the products under conditions where its formation is co~~sidered a measure of the K-atom concentration. The NO "titration" value, the maximum extent of HCN production fro111 C2M,, and the destruction of X H 3 after different times of decay of active nitrogen gave evidence that part of the NO reaction occurred, as does the NH:, reaction, xvith excited nitrogen molecules. The long lifetime of the N2* species capable of reaction with S O or NH3, as calc~~latecl from the abo\:e data, strongly favors its identification as low vibrational levels of the S2(A3Z,,+I molecule. A consideration of the values for the NO/HCN, NH3/HCN, and i\;H:,/i\;O ratios, after different times of decay, for poisoned ancl unpoisoned systems, suggested that the N?* responsible for the NH:, reaction is formed only during homogeneous recombination of N atoms, while the NY* responsible for reaction with NO might be produced by \\call recombination as ~vell. I'ossible reactions of excited molecules present in the active nitrogen -NO system that might lead to clecon~positio~i of XO without consumption of N atoms are discussed.

Abstract. Clouds are one of the main reasons of uncertainties in the forecasts of weather and climate. In part, this is due to limitations of remote sensing of cloud microphysics. Present approaches often use passive spectral measurements for the remote sensing of cloud microphysical parameters. Large uncertainties are introduced by three-dimensional (3-D) radiative transfer effects and cloud inhomogeneities. Such effects are largely caused by unknown orientation of cloud sides or by shadowed areas on the cloud. Passive groundbased remote sensing of cloud properties at high spatial resolution could be crucially improved with this kind of additional knowledge of cloud geometry. To this end, a method for the accurate reconstruction of 3-D cloud geometry from cloud radar measurements is developed in this work. Using a radar simulator and simulated passive measurements of model clouds based on a large eddy simulation (LES), the effects of different radar scan resolutions and varying interpolation methods are evaluated. In reality, a trade-off between scan resolution and scan duration has to be found as clouds change quickly. A reasonable choice is a scan resolution of 1 to 2 • . The most suitable interpolation procedure identified is the barycentric interpolation method. The 3-D reconstruction method is demonstrated using radar scans of convective cloud cases with the Munich miraMACS, a 35 GHz scanning cloud radar. As a successful proof of concept, camera imagery collected at the radar location is reproduced for the observed cloud cases via 3-D volume reconstruction and 3-D radiative transfer simulation. Data sets provided by the presented reconstruction method will aid passive spectral ground-based measurements of cloud sides to retrieve microphysical parameters.

The main features of the reactions of active nitrogen with various organic n~olecules are reviewed, and a unified mechanism outlined t o account for a t least the Inore significant experimental observations. INTRODUCTIONLewis (23) discovered active ilitrogeil in 1900. He observed that when nitrogen a t low pressure was subjected to a condensed discharge, a yellow mist filled the discharge tube and diffused into the connecting tubes. On breaking the current, a yellow afterglow persisted for several seconds. He showed that the afterglow gave a banded spectrum which could be identified with part of the N:! spectrum.In 1911, Strutt (later, Lord Rayleigh) began an extensive study of the physical and chemical properties of nitrogen treated by the Lewis method (12, 13, 34, 40 to 47). He found it to be very reactive chemically. Vapors of many metallic and non-metallic elements (e.g. cadmium, sodium, arsenic, sulphur) were converted to nitrides. Carbon disulphide, sulphur chloride, and hydrogen sulphide yielded a polymeric nitrogen sulphide. Hydrocarboils gave hydrogen cyanide as the main product, while halogenated hydrocarbons gave products from which cyailates were obtained by treatment with potassium hydroxide. All the reactions with organic compouilds were accompailied by the brilliant emissioil of the CN spectrum. The hydrocarboils gave both the red and violet C N bands and the flames appeared lilac in color. When halogen atoms were present in the molecule, the red bands were more strongly developed; this was particularly marked with CC14, CHC13, CHBr3, ethylene dichloride, and ethylidene chloride all of which gave strong orange cyanogen emission. Ethyl chloride and methyl bromide gave flames of intermediate character.Although most of the early studies of the chemical reactivity of active nitrogen were qualitative in nature (22, 53, 54) the reactions with hydrogen (6,22,39) and with nitric oxide and nitrogen dioxide (37) were studied in some detail. Reasonable mechanisms involving atomic nitrogen were suggested for these reactions.Investigations illto the reactioizs of active nitrogen with various types of molecules, particularly the hydrocarboils and chloriilated hydrocarbons, have been in progress in this laboratory during the past tell years. I t seems appropriate a t this time to review the maill characteristics of these reactions For personal use only.

Wleasurements of the rates of alkaline hydrolysis of cyclotrirnethylenetrinitrarnine (RDX) and cyclotetramethyle~~etetmnitramine (HMX) in aqueous acetone show these two reactions to involve consecutive steps, the first of which is seco~id order and rate controlling. Activation energies were estimated as 14 ant1 25 kcal. respectively. B y establishing calibratior~ curves, and controlling temperature, alkali concentration relative to concentration of esplosive,