Engineering Papers⌕ Search

Engineering topics

Anicich, V. G.

Publications and source records attributed to Anicich, V. G..

36 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Ion-molecule reactions in unsaturated hydrocarbons - Allene, propyne, diacetylene, and vinylacetylene

Ion-molecule reactions in allene, propyne, diacetylene, and vinylacetylene (1-buten-3-yne) have been studied at near-thermal energies by the technique of ion cyclotron resonance mass spectrometry. Rate coefficients and branching ratios are reported for the reactions of C3Hn(+) (n = 1-4) with allene and propyne and for the reactions of C4Hn(+) (n = 0-5) with diacetylene and vinylacetylene. Branching ratios are also given for the reactions of C4Hn(+), C5Hn and C6Hn(+) with propyne and for reactions of C6Hn(+) with diacetylene and vinylacetylene. More than 90 percent of the reactive channels lead to product ions having a larger carbon skeleton than the reactant ion. Evidence for ions with the same m/e ratio having differing reactivities was obtained for C3Hn(+), C6H7(+), and C7H7(+). Ion reaction sequences in allene and propyne were followed at higher pressures (0.0001 torr) to investigate secondary, tertiary, and higher order processes.

Anicich, V. G.↗
NASA NTRS1983

An ICR study of ion-molecule reactions of PH(n)+ ions

The reactions of PH(n)+ ions (n = 0-3) were examined with a number of neutrals using ion-cyclotron-resonance techniques. The reactions examined have significance for the distribution of phosphorus in interstellar molecules. The results indicate that interstellar molecules containing the P-O bond are likely to be more abundant than those containing the P-H bond.

Thorne, L. R.↗
NASA NTRS1982

Compact Ion Source for Mass Spectrometers

Cyclotron-resonance device uses miniature components and permanent magnet for small size, low weight, and low cost. Gas molecules are ionized by electrons from hot filament. Magnetic field, acting with electrostatic drift field, causes ions to move in circles with a superimposed drift perpendicular to both fields, toward the exit. Compact source can be used for studying ion-molecule reactions by ion cyclotron-resonance methods in conventional mass spectrometer with either magnetic sector or quadrupole sector.

Anicich, V. G.↗
NASA NTRS1981

An ICR investigation of ion-molecule reactions of HCN

Laboratory reaction rates and product distributions measured by the ion cyclotron resonance technique are reported for a series of reactions of HCN(+) ions with the neutral molecules HCN, CH4, NH3, H2O, CO, CO2, N2 and O2. Rate coefficients are also reported for reactions of positive ions derived from these molecules with HCN. A comparison of the results with a survey of literature values for rate coefficients of HCN(+) reactions shows some exothermic proton transfers from HCN(+) to be inefficient.

Mcewan, M. J.↗
NASA NTRS1980

Laboratory studies of some of the major ion-molecule reactions occurring in cometary comae

Laboratory results have been obtained for some of the key ion-molecule reactions which should occur in the inner coma of comets. A complete listing is given of laboratory data presently available for ion-molecule reactions occurring in a mixture of H2O, CO2, CO, CH4, N2, and NH3 cometary volatiles. From these data, the most important reactions occurring in the coma of a water-dominated comet are extracted for use in models of the physics and chemistry of cometary comae.

Huntress, W. T., Jr.↗
NASA NTRS1980

Miniature cyclotron resonance ion source using small permanent magnet

An ion source using the cyclotron resonance principle is described. A miniaturized ion source device is used in an air gap of a small permanent magnet with a substantially uniform field in the air gap of about 0.5 inch. The device and permanent magnet are placed in an enclosure which is maintained at a high vacuum (typically 10 to the minus 7th power) into which a sample gas can be introduced. The ion beam end of the device is placed very close to an aperture through which an ion beam can exit into the apparatus for an experiment.

Anicich, V. G.↗
NASA NTRS1980

An ICR study of ion-molecule reactions in the C2H2/HCN system

Using the ICR technique, rate constants are obtained for the reaction of C2H2(+) with HCN and of HCN(+) with C2H2. They are, respectively, 3.6 x 10 to the -10 cu cm/molecule-s and 6.9 x 10 to the -10 cu cm/molecule-s. Discrepancies between these results and other measurements of the first reaction are discussed. The relevance of this reaction to the formation of HC3N in interstellar clouds is considered.

Mcewan, M. J.↗
NASA NTRS1980

An ICR study of an association reaction at low pressure

The reactions of the gaseous ion CH3+ with HCN are investigated, using the ion cyclotron resonance technique. The pressure range of the experiment was 1 x 10 to the -6 to 3 x 10 to the -4 Torr with a rate coefficient of 2 x 10 to the -10 cu cm/sec. Good agreement was found between rate coefficients determined in the trapping mode at the low end of the pressure range and the drift mode at the high end of the pressure range. It is shown that the association reaction of CH3 with HCN follows second order kinetics throughout the entire pressure range of the experiment. The reaction is interpreted in terms of both a saturated three-body and a radiative association mechanism. Some explanations for the disagreement of the rate coefficient with that reported previously are also given.

Mcewan, M. J.↗
NASA NTRS1978

An ion cyclotron resonance study of reactions of some atomic and simple polyatomic ions with water

Reactions of various positive ions with water vapor were studied by ion cyclotron resonance mass spectrometric techniques. Rate constants and product distributions were determined for reactions of the ions: Ar(+), Co(+), N2(+), and CO2(+), CH2(+), and CH4(+), CH2Cl(+), HCO(+), H2CO(+), H2COH(+), H2S(+) and HS(+). The results obtained in this work are compared with earlier reported data where available.

Karpas, Z.↗
NASA NTRS1977

Product distributions for some thermal energy charge transfer reactions of rare gas ions

Ion cyclotron resonance methods were used to measure the product distributions for thermal-energy charge-transfer reactions of He(+), Ne(+), and Ar(+) ions with N2, O2, CO, NO, CO2, and N2O. Except for the He(+)-N2 reaction, no molecular ions were formed by thermal-energy charge transfer from He(+) and Ne(+) with these target molecules. The propensity for dissociative ionization channels in these highly exothermic charge-transfer reactions at thermal energies contrasts with the propensity for formation of parent molecular ions observed in photoionization experiments and in high-energy charge-transfer processes. This difference is explained in terms of more stringent requirements for energy resonance and favorable Franck-Condon factors at thermal ion velocities.

Anicich, V. G.↗
NASA NTRS1977

Ion cyclotron resonance studies of some reactions of N/+/ ions

Product distributions and rate constants for the reactions of ground-state N(+) ions with CO, NO, CO2, and CH4 were measured. Rate constants were obtained using ion-cyclotron-resonance trapped-ion methods, and product distributions were obtained using a tandem (Dempster-ICR) mass spectrometer. Rapid nitrogen isotope exchange was also observed in N(+)-N2 collisions.

Anicich, V. G.↗
NASA NTRS1977

Calibration of marginal oscillator sensitivity for use in ICR spectrometry

A constant-reference load is utilized as Q-spoiler in calibrations of relative sensitivity variations of a marginal oscillator with frequency. Frequency-dependent effects troublesome in earlier Q-spoilers are compensated by employing a pure resistive calibration load with compensation for the small distributed capacitance of large resistors. The validity of the approach is demonstrated for a 2:1 mass ratio range, and validity for a mass ratio range greater than 10:1 is claimed. The circuit and technique were developed for use in ion cyclotron resonance (ICR) spectrometric practice.

Anicich, V. G.↗
NASA NTRS1976

On the reaction of N/+/ ions with O2

The reaction of atomic nitrogen ions with molecular oxygen is a major loss mechanism for N(+) ions in the ionosphere and is a source of NO(+) ions and atomic nitrogen at certain altitudes. Ion cyclotron resonance methods are used to measure the product distribution of thermal energy N(+) ions reacting with O2. Three product channels are identified with the following fractional distributions: O2(+) + N, 0.65 plus or minus 0.04; NO(+) + O, 0.31 plus or minus 0.04; O(+) + NO, 0.04 plus or minus 0.02.

Huntress, W. T., Jr.↗
NASA NTRS1976

Ion cyclotron resonance studies of some reactions of C/+/ ions

Product distributions and rate constants for the reaction of ground state C(+) ions with O2, NO, HCl, CO2, H2S, H2O, HCN, NH3, CH4, H2CO, CH3OH, and CH3NH2 have been measured. Rate constants were obtained using ion cyclotron resonance trapped ion methods, and product distributions were obtained using a tandem mass spectrometer. Rapid carbon isotope exchange has also been observed in C(+)-CO collisions.

Anicich, V. G.↗
NASA NTRS1976

Measurement and significance of the equilibrium reaction C-13/+/ + /C-12/O yields C-12/+/ + /C-13/O for alteration of the C-13/C-12 ratio in interstellar molecules

Laboratory measurements using the ion-cyclotron resonance technique yield a rate constant of 2 by 10 to the -10th power cu cm/sec at 300 K for the isotope exchange C-13(+) + (C-12)O yields C-12(+) + (C-13)O. According to the usual ideas about ion-molecule reactions, this rate constant should also be appropriate at temperatures not exceeding about 100 K. Then the observed C-13/C-12 ratio obtained from radio observation of interstellar molecules may be either larger or smaller than the actual value in the interstellar medium by factors of 2 or so. If the ratio is altered from the actual interstellar value, it will not be the same in all molecules, and CO will tend to have the highest value. The chief astronomical uncertainty for the occurrence of this isotope fractionation is the abundance of 'unobservable' molecules which can react rapidly with C(+): e.g., O2, H2O, CO2, and CH4. If their abundance is greater than about one-tenth that of CO, the isotope fractionation will be inhibited.

Watson, W. D.↗