Trace explosives signatures of TNT and DNT have been extracted from multiple sediment samples adjacent to unexploded undersea ordnance at Halifax Harbor, Canada. The ordnance was hurled into the harbor during a massive explosion some 50 years earlier, in 1945 after World War II had ended. Laboratory sediment extractions were made using the solid-phase microextraction (SPME) method in seawater and detection using the Reversal Electron Attachment Detection (READ) technique and, in the case of DNT, a commercial gas chromatograph/mass spectrometer (GC/MS). Results show that, after more than 50 years in the environment, ordnance that appeared to be physically intact gave good explosives signatures at the parts per billion level, whereas ordnance that had been cracked open during the explosion gave no signatures at the 10 parts per trillion sensitivity level. These measurements appear to provide the first reported data of explosives signatures from undersea unexploded ordnance.

A concept for a passive neutral gas concentrator that facilitates the analysis of rarefied atmospheres using mass spectrometry on spacecraft has been developed. The efficiency of the concentrator depends strongly on gas–surface scattering dynamics between the incoming gas molecules and the concentrator surface. We conducted beam–surface scattering experiments using hyperthermal beams containing atomic and molecular oxygen with speeds of approximately 5500 m s–1, with angular and velocity resolution of the inelastically scattered O and O2, on gold thin film, SiO2, and highly oriented pyrolytic graphite (HOPG) surfaces, which were chosen as candidate concentrator surfaces. The results show clearly that atoms and molecules scattering from HOPG have the narrowest and most superspecular angular distributions with the least energy transferred to the surface. A test particle model, referred to as the Statistical Program for Aerodynamic and Radiation Pressure Coefficient Simulation, utilized the experimental results to model gas concentration in three-dimensional cone and annular-ring geometries constructed of the representative materials chosen for study. The modeling results indicate that a cone concentrator with a 10° half angle opening yields the highest concentration factors. In addition, a cone constructed of HOPG yields a concentration factor that is an order of magnitude higher than what can be achieved using gold or SiO2 surfaces.

On page 38, line 20, units of is printed as (rad)15 1, it should have been printed as (rad s 1. On page 39, line 51, the text was incorrectly printed as follows: 'This leads to an avoidable acceleration of the electron beam, and to a different ionisation impact cross-section (and branching fractions) than encountered for the case of the NIST tabulation at the standard 70 eV ionisation energy' The text should have been printed as: 'This leads to an unavoidable acceleration of the electron beam, and to a different ionisation impact cross-section (and branching fractions) than encountered for the case of the NIST tabulation at the standard 70 eV ionisation energy'. The publishers apologize for these errors.

Carbon dioxide has been produced from the impact of a monoenergetic O( 3 P) beam upon a surface cooled to 4.8 K and covered with a CO ice. Using temperature-programmed desorption and mass spectrometer detection, we have detected increasing amounts of CO 2 formation with O( 3 P) energies of 2, 5, 10, and 14 eV. This is the first measurement of polyatomic molecule formation on a surface with superthermal atoms. The goal of this work is to detect other polyatomic species, such as CH 3 OH, which can be formed under conditions that simulate the grain temperature, surface coverage, and superthermal atoms present in shock-heated circumstellar and interstellar regions.

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