A molecular beam study of the reaction K+CH3I→ KI+CH3 over an extended range of collision energy is described. A thermal K beam is crossed with a seeded supersonic nozzle beam of CH3I. The excitation function (energy dependence of the reaction cross section) for this reaction was measured from 0.1 to 1 eV (c.m.). The total flux of the KI reaction product was determined by integration over the laboratory spherical polar coordinates (Θ,  Φ) of the in-plane and out-of-plane angular distributions of KI measured by a two-filament differential surface ionization detector mounted on a goniometer. By seeding the CH3I with a variety of lighter gases, its velocity could be changed from δ ≈ 530–2330  m/sec. The average center of mass collision energy, Ē, was thereby varied from 0.1 to 1 eV. The densities of both beams were monitored during the scattering experiments, so that relative cross sections vs Ē were obtained with a precision of ≈ ± 10%. The supersonic CH3I beam speed distributions were quite narrow (FWHM ≈ 20%). The K speed distribution was essentially Maxwellian. The measured total reaction cross section rises to a maximum at Ē=0.18(± 0.03)  eV, beyond which it decreases continuously. No evidence was found for the occurrence of additional (high energy) processes, such as chemiionization or formation of alternative products.

A new optical hydrogen sensor based on spontaneous Raman scattering of laser light has been designed and constructed for rugged field use. It provides good sensitivity (better than 100 parts in 10(6)), rapid response (several seconds), and the inherent Raman characteristics of linearity and background gas independence of the signal. Efficient light collection and discrimination by using fast optics and a bandpass interference filter compensate for the inefficiency of the Raman-scattering process. A multipass optical cavity with a Herriott-type configuration provides intense illumination from an air-cooled cw gas laser. The observed performance is in good agreement with the theoretical signal and noise level predictions.

A high temperature flow reactor has been constructed to perform kinetic and spectroscopic studies on species at temperatures between 300 and 1500 K. The species in the flow reactor may be detected or studied using: laser-induced fluorescence, resonance fluorescence, infrared absorption, ultraviolet absorption, chemiluminescence, or molecular beam mass spectrometry. The features of the apparatus are described in detail, and the initial spectroscopic and kinetic studies are discussed.

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Groundbased and onboard video images of a sunlit Shuttle Orbiter water dump are interpreted as showing that the continuous ∼1 mm diameter liquid stream quickly breaks up in near‐vacuum to form ice/snow particles of two characteristic sizes. Discrete large droplets (shown from laboratory measurements, to have diameters comparable with that of the initial coherent quasicylinder) are most evident in the close‐in photographs, and unresolved submicron “fog” from recondensation of overexpanded evaporated water appears to dominate the ground‐telescope photographs of the ∼2½ km long optically detectable trail. We estimated the mean diameter of the smaller particles from the spatial distribution of visible radiance using a model of their energy balance, (small) surface roughening as they sublime, and Mie scattering of pre‐dawn sunlight. The results are consistent with those from recent space‐tank simulations.