Engineering topics
Orient, O. J.
Publications and source records attributed to Orient, O. J..
Reply to the Comments of Chu et al. on O.J. Orient and A. Chutjian, in Physical Review Letters 74, 5017 (1995)
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Study of Dissociative Electron Attachment and Ion-Pair Channels In H-/H2
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Miniature, High Resolution, Quadrupole Mass Spectrometer Array
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Miniature, High-Resolution Quadrupole Mass-Spectrometer Array: Applications to Environmental Monitoring and Control
A miniature quadrupole mass spectrometer array has been designed and tested. It consists of 16 rods in a 4x4 array.
A LIGA Fabricated Quadrupole Array for Mass Spectroscopy
A linear array of nine quadrupoles was fabricated using the LIGA process. Pole heights ranging from 1 to 3 mm were fabricated using synchrotron X-ray exposures to form free standing polymethylmethacrylate (PMMA) molds into which copper, gold or nickel were electroplated.
Electron-Impact Dissociation and Ionizatin Channels in H(sub 2)
Dissociative electron attachment (DA) to H(sub 2) has been studied by measuring the outgoing kinetic energies of the H- with H in the various final channels.
Miniature, High-Resolution, Quadrupole Mass Spectrometer Array
A minature quadrupole mass-spectrometer array consisting of 16 rods in a 4X4 array is reported.
Detection of New Dissociative Electron Attachment Channels in NO
Three dissociative electron attachment channels have been detected and identified in NO via measurement of the O minus (exp 2)P fragment energy. In addition to the known N((exp 2 D(exp 0)) + O minus (exp 2)P channel, two new channels N((exp 1 S(exp 0)) + 0 (2 P) and N(exp 2)P(exp 0) + O(exp 2)P were detected. Cross sections for each of the channels are reported by normalizing the scattering intensities to previously measured total cross sections. The experimental approach uses solenoidal magnetic confinement of the electrons and ions, and trochoidal energy analysis of the low-energy ions.
Detection of New Dissociative Attachment Channels in NO
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Observation of CH A2 - X2, and B2 - X2, Emissions in Gas-Phase Collisions of Fast O(3P) Atoms
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Observation of CH A (sup 2)Delta approaches X (sup 2)Pi(sub r) and B (sup 2)Sigma(sup -) approaches X (sup 2)Pi(sub r) emissions in gas-phase collisions of fast O((sup 3)P) atoms with acetylene
Optical emissions in single-collision, beam-beam reactions of fast (3-22 eV translational energy) O(P-3) atoms with C2H2 have been measured in the wavelength range 300-850 nm. Two features were observed, one with a peak wavelength at 431 nm, corresponding to the CH A (sup 2)Delta yields X (sup 2)Pi(sub r) transition, and a second weaker emission in the range 380-400 nm corresponding to the B (sup 2)Sigma(sup -) yields X (sup 2)Pi(sub r) transition. Both the A yields X and B yields X emissions were fit to a synthetic spectrum of CH(A) at a vibrational temperature T(sub v) of 10,000 K (0.86 eV) and a rotational temperature T(r) of approximately 5000 K (0.43 eV); and CH(B) to T(sub v) = 2500 K (0.22 eV) and T(sub r) = 1000 K (0.09 eV). The energy threshold for the A yields X emission was measured to be 7.3 +/- 0.4 eV (lab) or 4.5 +/- 0.2 eV (c.m.). This agrees with the energy threshold of 7.36 eV (lab) for the reaction O(P-3) + C2H2 yields CH(A) + HCO.
Optical Emissions Observed in Collisons of Fast 0(3P) Atoms with Gas-Phase and Surface-Adsorbed Species
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Effect of trapped ions in a gated time-of-flight apparatus
A three-mesh gate is used in a time-of-flight (TOF) apparatus to analyze the velocity of positive ions. Test results and a theoretical description are presented of an effect arising from trapping ions between meshes of a two-gate TOF velocity analyzer. The entrapped ions produce a side peak in the TOF spectra corresponding to faster ions. The onset and relative height of the side peak is dependent on the gating voltage and risetime of the pulsing electronics, while the relative intensity depends upon the velocity being sampled and the ratio of the gate width to duration.
Observation of CN Z - X and B - X emissions in gas-phase collisions of fast O(3P) atoms with HCN
Studies of spacecraft surfaces in LEO have shown that CN(B - X) emission occurs when the spacecraft shuttle engine exhaust species collide with the atmosphere. A study of the reaction of fast O(3P) atoms with HCN under single-collision conditions is reported. The channels active in the hyperthermal energy regime are identified as CN(B 2Sigma(+) - X 2Sigma(+)) and CN(A 2Pi(i) - X 2Sigma(+)) transitions. The experimental B - X vibrational bands fit a synthetic spectrum of CN at a vibrational temperature of 7000 K and a rotational temperature of 2000 K. The CN(B - X) emission is observed when spacecraft shuttle-engine exhaust species collide with the atmosphere.
Theory and operation of a three-gate time-of-flight velocity analyzer
Theoretical considerations and test results are presented for a new-type velocity analyzer for incident fast neutral particles, positive ions, and negative ions. Velocity analysis is carried out by means of a pulsed, three-gate time-of-flight (TOF) technique capable of eliminating alias velocities (harmonics) to sixth order. In addition the design and operation are presented of a four-element ion lens system, with small spherical and chromatic aberrations, suitable for interfacing a large-diameter ion beam from the TOF section with a subsequent mass analyzer.
Optical emission generated by collisions of 5 eV O(3P) atoms with surface-absorbed hydrazine
Optical emission has been observed corresponding to vibrational bands in the NH (A 3Pi - X 3Sigma(-)) electronic transition during collisions of 5 eV, ground-state oxygen O(3P) atoms with MgF2 and Ni surfaces continuously exposed to a beam of hydrazine (N2H4). The NH emission intensity is observed to be about five times greater for MgF2 than for Ni. No dependence on temperature was observed for either surface in the range 240 - 340 K, implying that the NH-producing intermediate species is tightly bound. The half-lifetime for desorption of hydrazine from each surface was measured. This was found to be 120 min for the MgF2 surface at 240 K, and less than 20 min for Ni. After exposure, the surface composition was measured using X-ray photoelectron spectroscopy on the exposed and unexposed areas of both targets.
Recombination of 5-eV O(3P) atoms with surface-adsorbed NO - Spectra and their dependence on surface material and temperature
Measurements have been conducted of the 300-850 nm recombination spectra associated with 5-eV collisions of O(3P) atoms with NO adsorbed on surfaces of MgF2, Ni, and Ti. Attention is given to the dependence of chemiluminescence intensity on surface temperature over the 240-340 K range. While all three materials tend to emit at the lower temperatures, MgF2 exhibits the greatest tendency to chemiluminescence. Both results are reflective of the greater packing density of surface-adsorbed NO at the lower temperatures for each surface. The activation energy for each surface is independent of emission wavelength, so that the same species is emitting throughout the wavelength range.