CHEMICAL SCAVENGER PROBE STUDIES OF ATOM AND EXCITED MOLECULE REACTIVITY IN ACTIVE NITROGEN FROM A SUPERSONIC STREAM

1964 ◽  
Vol 42 (11) ◽  
pp. 2440-2450 ◽  
Author(s):  
A. Fontijn ◽  
D. E. Rosner ◽  
S. C. Kurzius
Keyword(s):  
Relative Concentration ◽  
Measurement Techniques ◽  
Supersonic Nozzle ◽  
Active Species ◽  
Discharge Zone ◽  
Supersonic Stream ◽  
Active Nitrogen ◽  
Local Composition ◽  
End Point ◽  
Excited Molecules

A quartz chemical scavenger probe has been developed to study the local composition of supersonic electrically discharged gas streams. The probe samples the central portion of a nonequilibrium jet and allows direct comparison with other local measurement techniques (e.g. differential catalytic detectors) for determining active species concentrations. Active nitrogen from a Mach 3 stream was sampled and reacted inside the probe with one of the scavenger gases NO, NH3, or C2H4 at 18.8 mm Hg and at an average temperature of 500 °K. Limiting values of the NO destruction rate and the HCN production rate were observed; however, NH3 destruction exhibited no plateau. The observed maximum rate of NO destruction was 2.1 times as large as the NO flow rate at the light titration end-point. This difference is attributed to a reaction of NO, added in excess of the titration end-point flow, with metastable electronically excited molecules formed within the discharge zone. The converging-diverging supersonic nozzle-glow discharge source used in these experiments apparently delivers metastable excited molecules to the reaction zone in a higher relative concentration than do the more conventional subsonic electrical discharge flow systems used for most previous active nitrogen studies.

THE REACTIVE COMPONENTS IN ACTIVE NITROGEN AND THE ROLE OF SPIN CONSERVATION IN ACTIVE NITROGEN REACTIONS

1956 ◽  
Vol 34 (9) ◽  
pp. 1217-1231 ◽  
Author(s):  
H. G. V. Evans ◽  
C. A. Winkler
Keyword(s):  
Experimental Information ◽  
Active Species ◽  
Convincing Evidence ◽  
Critical Examination ◽  
Vibrationally Excited ◽  
Active Nitrogen ◽  
Electronically Excited ◽  
Excited Molecules ◽  
Triatomic Radicals

Critical examination of the available experimental information provides rather convincing evidence that atomic nitrogen is the main reactive species in active nitrogen. It appears quite unlikely that a significant contribution to the activity is made by electronically excited molecules, metastable atoms, ions, or triatomic radicals. Evidence exists, however, for the presence of more than one active species, and a plausible suggestion would seem to be that the second species is vibrationally excited molecules. Consideration of the role of spin conservation in reactions of active nitrogen leads to the conclusion that reactions that conserve spin occur more readily than those in which spin is not conserved.

CATALYZED RECOMBINATION OF NITROGEN ATOMS, AND THE POSSIBLE PRESENCE OF A SECOND ACTIVE SPECIESIN ACTIVE NITROGEN

1960 ◽  
Vol 38 (12) ◽  
pp. 2514-2522 ◽  
Author(s):  
Roger Kelly ◽  
C. A. Winkler
Keyword(s):  
Rate Constant ◽  
Pressure Range ◽  
Order Rate Constant ◽  
Active Species ◽  
Third Order ◽  
Active Nitrogen ◽  
Atom Concentration ◽  
Order Rate ◽  
Excited Molecules ◽  
Atom Decay

The reactions of ethylene, ethane, and ammonia with active nitrogen have been studied over the pressure range 0.3 to 4 mm usinganunheatedreaction vessel. The object was to determine why each reactant shows, as is well-known, a smaller extent of reaction at lower temperatures than would be predicted from the atom concentration. It was concluded that ethylene probably brought about homogeneouscatalyzedrecombination, i.e. the process [Formula: see text] followed by N + N•C2H4 → N2 + C2H4. The over-all third-order rate constant appeared to be very large, about 1.8 × 10−28 cc2 molecule−2 sec−1. The behavior of ammonia was quite different from that of ethylene and it was, in fact, possible to show that the extent of reaction was not governed by the instantaneous atom concentration at all. The results can be explained qualitatively, however, if it is assumed that excited molecules formed in the course of homogeneous atom decay constitute a second active species in active nitrogen. This view serves also to explain the failure in such work as that of Kistiakowsky etal. to observe ammonia destruction or excited molecules when especially low atom concentrations are used. The few experiments involving ethane were sufficient to show that the reactivity was low for a different reason than with ethylene.

The Need for Microstructural Measurement Techniques in the Study of Cosmetic Product Properties

MRS Bulletin ◽  
2007 ◽  
Vol 32 (10) ◽  
pp. 793-800
Author(s):  
P. G. Cummins ◽  
C. Fthenakis
Keyword(s):  
Small Molecules ◽  
Measurement Techniques ◽  
Active Species ◽  
Clear Understanding ◽  
Interfacial Interactions ◽  
Product Property ◽  
Chemical Systems ◽  
Cosmetic Product ◽  
Cosmetic Industry ◽  
Surface Active

AbstractA cosmetic product is often a complex non-homogeneous mixture of physicochemical units including polymers, small molecules, surface-active species, and particles. In use, it is applied to an equally heterogeneous substrate, skin. Consequently, materials structure as well as composition and the nature of the surfaces are relevant to a clear understanding of any technologically important product property or process. No longer is it sufficient to answer the classical questions of analysis—what and how much?—for many applications; we must now ask the additional questions of where, how organized, and how is it manifest to the customer? Although analytical sciences have, for many years, been applied to the problem of characterizing what is in chemical systems, the need to understand spatial and interfacial interactions has received much less attention. The explosive growth, however, in electronics, computing, biology, mathematical methodologies, microscopy, and optics now present the cosmetic industry with a new set of tools that can be utilized to address this issue. It is the objective of this article to highlight some of these measurement advances and how they might have relevance in the cosmetics industry in the coming years.

scholarly journals Influence of Active Nitrogen Species on the Nitridation Rate of Sapphire

1998 ◽  
Vol 537 ◽  
Author(s):  
A.J. Ptak ◽  
K.S. Ziemer ◽  
M.R. Millecchia ◽  
C.D. Stinespring ◽  
T.H. Myers
Keyword(s):  
Molecular Nitrogen ◽  
Active Species ◽  
Operating Conditions ◽  
Rf Plasma ◽  
Atomic Nitrogen ◽  
Active Nitrogen ◽  
Plasma Sources ◽  
Electrostatic Deflector ◽  
Low Energy Ions ◽  
Operating Regimes

AbstractThe operating regimes of two rf-plasma sources, an Oxford CARS-25 and an EPI Unibulb, have been extensively characterized. By changing the exit aperture configuration and using an electrostatic deflector, the Oxford source could produce either primarily atomic nitrogen, atomic nitrogen mixed with low energy ions, or a large flux of higher energy ions (>65eV) as the active species in a background of neutral molecular nitrogen. The EPI source produced a significant flux of metastable molecular nitrogen as the active species with a smaller atomic nitrogen component. Nitridation of sapphire using each source under the various operating conditions indicate that the reactivity was different for each type of active nitrogen. Boron contamination originating from the pyrolytic boron nitride plasma cell liner was observed.

Kinetics of reactions involving CN emission III. The excitation of CN in active nitrogen

1968 ◽  
Vol 305 (1480) ◽  
pp. 93-105 ◽  
Keyword(s):  
Ground State ◽  
Blue Emission ◽  
Absolute Intensity ◽  
Active Species ◽  
Active Nitrogen ◽  
System A ◽  
Vibrational Levels ◽  
Similar Quantity ◽  
Kinetics Of ◽  
Cn Radicals

The presence of carbonaceous impurities in active nitrogen causes strong blue CN emission from levels of the B 2 ∑ + state up to v ' = 15. The kinetics of this emission have been studied, and the concentrations of CN radicals measured by electronic absorption spectroscopy, in systems where the blue emission was induced by adding traces of methane before the discharge, or a similar quantity of acetylene after the discharge and examining the system a long way downstream. CN is shown to be excited by energetic species formed in nitrogen atom recombination. The absolute intensity of the emission and its kinetics suggest that lower vibrational levels of the metastable A 3 ∑ + state of N 2 are mainly responsible, but the kinetics of quenching by ammonia and water for nitrogen and argon carriers show that an additional active species is present, probably N 2 in high vibrational levels of the ground state.

Influence of Nitrogen Species on InN Grown by PAMBE

2005 ◽  
Vol 892 ◽  
Author(s):  
P. A. Anderson ◽  
R. J. Kinsey ◽  
C. E. Kendrick ◽  
I. Farrel ◽  
D. Carder ◽  
...  
Keyword(s):  
Emission Spectroscopy ◽  
Molecular Nitrogen ◽  
Optical Emission ◽  
Lattice Relaxation ◽  
Plasma Source ◽  
High Energy ◽  
Active Species ◽  
Nitrogen Species ◽  
Active Nitrogen ◽  
Molecular Flux

AbstractActive nitrogen species produced by an Oxford Applied Research HD-25 plasma source have been monitored by optical emission spectroscopy and quadrapole mass spectroscopy. Both techniques confirmed that at higher RF powers and lower flow rates the efficiency of atomic nitrogen production increased; emission spectroscopy confirmed that this was at the expense of active molecular nitrogen (N2*). InN films grown on (0001) sapphire/GaN with higher relative molecular content were found to have lower carrier concentrations than the corresponding films grown with higher atomic content. However, electrical properties of films grown on (111) YSZ showed insensitivity to the active nitrogen content. Etching experiments revealed that films grown on sapphire/GaN were nitrogen-polar, while films grown on YSZ were In-polar, suggesting that film polarity can greatly influence the effect active species have on growth. Lattice relaxation, as measured by reflection high-energy electron diffraction, revealed that the N-polar films grown under high relative molecular flux relaxed fully after ∼60 nm of growth, while the corresponding In-polar film relaxed fully within the first several nm of growth.

THE REACTION OF ACTIVE NITROGEN WITH MIXTURES OF ETHYLENE AND NITRIC OXIDE

1965 ◽  
Vol 43 (7) ◽  
pp. 1899-1904 ◽  
Author(s):  
E. Fersht ◽  
R. A. Back
Keyword(s):  
Nitric Oxide ◽  
Nitrogen Atom ◽  
Active Nitrogen ◽  
Atom Concentration ◽  
Condensed Discharge ◽  
Excited Molecules ◽  
True Measure ◽  
Concerted Reaction

The reaction of active nitrogen, produced in a condensed discharge at 1 mm pressure, with mixtures of ethylene and nitric oxide has been studied with mixtures ranging in composition from pure ethylene to pure nitric oxide. The sum of HCN + 14N16N produced from mixtures of C2H4 and 15NO remained constant and equal to the HCN produced from pure C2H4 for NO concentrations up to 50 mole %. As more NO was added, this sum rose towards the value of 14N15N produced from pure 15NO. These data appear to lend support to the HCN yield from ethylene as the true measure of nitrogen atom concentration. It is suggested that 15NO also undergoes a concerted reaction with excited 14N14N molecules, probably in the A3 Σu+ state, to produce 14N15N, and that these excited molecules can be quenched by collision with ethylene or methane without consuming nitrogen or forming HCN.

scholarly journals Influence of Active Nitrogen Species on the Nitridation Rate of Sapphire

1999 ◽  
Vol 4 (S1) ◽  
pp. 161-166 ◽  
Author(s):  
A.J. Ptak ◽  
K.S. Ziemer ◽  
M.R. Millecchia ◽  
C.D. Stinespring ◽  
T.H. Myers
Keyword(s):  
Molecular Nitrogen ◽  
Active Species ◽  
Operating Conditions ◽  
Rf Plasma ◽  
Atomic Nitrogen ◽  
Active Nitrogen ◽  
Plasma Sources ◽  
Electrostatic Deflector ◽  
Low Energy Ions ◽  
Operating Regimes

The operating regimes of two rf-plasma sources, an Oxford CARS-25 and an EPI Unibulb, have been extensively characterized. By changing the exit aperture configuration and using an electrostatic deflector, the Oxford source could produce either primarily atomic nitrogen, atomic nitrogen mixed with low energy ions, or a large flux of higher energy ions (>65 eV) as the active species in a background of neutral molecular nitrogen. The EPI source produced a significant flux of metastable molecular nitrogen as the active species with a smaller atomic nitrogen component. Nitridation of sapphire using each source under the various operating conditions indicate that the reactivity was different for each type of active nitrogen. Boron contamination originating from the pyrolytic boron nitride plasma cell liner was observed.

Plasma Nitriding Mechanisms of Low-Density Sintered Metal Products

2021 ◽  
Vol 76 (1) ◽  
pp. 58-63
Author(s):  
E. Roliński ◽  
M. Woods
Keyword(s):  
Formation Mechanism ◽  
Plasma Nitriding ◽  
Active Species ◽  
Low Density ◽  
Nitrogen Species ◽  
Powder Metal ◽  
Active Nitrogen ◽  
Sintered Metal ◽  
Metal Plasma ◽  
Metal Products

Abstract The mechanism of plasma nitriding include the formation of various active species generating nitrogen atoms reacting with the metal. Which species prevail in supplying nitrogen depends on nitriding conditions as well as the nature of the treated metal. Plasma nitriding of low-density powder metal (PM) products results in a formation of the layers whose thicknesses may depend on the gas pressure used for the process. Higher pressure can cause locally deeper penetration of the surface by active nitrogen species formed from ammonia compounds generated by the plasma. While a low processing pressure reduces this effect significantly. The formation mechanism of a locally thicker layer relies on the presence of open porosities in the surface as they can be penetrated by the ammonia species generated by the plasma. The same porosities cannot be penetrated by the ions of nitrogen formed at the same time since their mean free life is much shorter than that of ammonia species. ◼

EXCITED MOLECULES AS THE REACTIVE SPECIES IN ACTIVE NITROGEN

1954 ◽  
Vol 32 (4) ◽  
pp. 399-403 ◽  
Author(s):  
R. A. Back ◽  
Margaret Menzies ◽  
C. A. Winkler
Keyword(s):  
Thermal Decomposition ◽  
Reactive Species ◽  
Active Nitrogen ◽  
Electronic Level ◽  
Decomposition Reactions ◽  
Condensed Discharge ◽  
Excited Molecules

No reaction has been detected between ethylene and nitrogen molecules obtained in the thermal decomposition of metallic azides. Since such decomposition reactions apparently produce nitrogen molecules excited to the same electronic level as those present in active nitrogen formed by a condensed discharge, it might be inferred that excited molecules are not the reactive species in active nitrogen.

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