Absolute number density and kinetic analysis of the CF radical in pulsed CF4+ H2radio-frequency plasmas

2012 ◽  
Vol 21 (2) ◽  
pp. 024008 ◽  
Author(s):  
S Stepanov ◽  
J Meichsner
Keyword(s):  
Kinetic Analysis ◽  
Absolute Number ◽  
Number Density

The Measurement of f-values for Lines of Astrophysical Interest by Beam-Foil Spectroscopy

1978 ◽  
Vol 3 (4) ◽  
pp. 263-264
Author(s):  
J. E. Ross ◽  
B. J. O’Mara
Keyword(s):  
Life Time ◽  
Absolute Number ◽  
Branching Ratios ◽  
Oscillator Strengths ◽  
Separate Experiment ◽  
Number Density ◽  
Reasonable Accuracy ◽  
Initial Excitation ◽  
The One ◽  
Beam Foil

The necessity of having accurate oscillator strengths in astrophysical applications is well known. The apparent discrepancy which existed between the solar and meteoritic abundance of iron is just one example of the problems which can arise from poor f-values. An excellent critique of methods for determining both absolute and relative f-values has been given by Blackwell & Collins (1972). Their comments on life-time techniques provide a clear indication of both the advantages and difficulties associated with these techniques: “In principle, a life-time method, as exemplified by the technique of beam foil spectroscopy, described for example by Wiese (1970), has the fundamental advantage that in some restricted circumstances its application does not depend upon a temperature measurement or any assumption of themodynamic equilibrium in the source: in addition it gives an absolute result without the need of an absolute number density of atoms. The hope is sometimes expressed that the method of beam foil spectroscopy will yield oscillator strengths of the required accuracy. In practice, the technique suffers from the difficulty that although the life-time of an excited state can be measured with reasonable accuracy, it is also necessary to measure in a separate experiment the branching ratios for radiative de-excitation. As these ratios are usually measured by an arc method, the accuracy of the final oscillator strengths is limited by the deficiencies of this source. Also, some atoms in the beam may be excited to higher levels than the one being examined, and because of the nature of the initial excitation is unknown, radiative de-excitation (cascading) takes place to this lower level in a way that is wholly unpredictable. This difficulty is especially important for levels of low excitation.” In this talk techniques will be described for overcoming the cascading problem in beam foil spectroscopy and for measuring the associated branching ratios.

Estimation of Absolute Number Densities from Shapes of Atomic Fluorescence Curves of Growth

1987 ◽  
Vol 41 (4) ◽  
pp. 613-620 ◽  
Author(s):  
B. W. Smith ◽  
M. J. Rutledge ◽  
J. D. Winefordner
Keyword(s):  
Spectral Width ◽  
Absolute Number ◽  
General Purpose ◽  
Number Density ◽  
Density Region ◽  
Atomic Fluorescence ◽  
Damping Parameter ◽  
Wide Range ◽  
Order Of Magnitude ◽  
General Purpose Computer

A general-purpose computer program has been developed to calculate atomic fluorescence curves of growth (COG) for a wide variety of cases and particularly for the experimentally interesting cases where the excitation source spectral bandwidth is not much different from the absorption linewidth in typical flames and plasmas. Calculations over a wide range of the variables which affect the shape of the COG in the high-number-density region show that the point of departure from linearity can be used to predict the absolute number density in the atomizer cell. For resonance atomic fluorescence, the point at which the experimental curve of growth is twofold below the low-density linear asymptote invariably occurs at a k0 L (peak absorption coefficient × absorption pathlength) product of 2 ± 1. Number densities can easily be determined to within an order of magnitude accuracy, even when such variables as source spectral width, collection geometry, and damping parameter are totally unknown. In favorable circumstances, where such variables are well known, accuracies of ±10% may be obtained. The calculated curves of growth are in excellent agreement with several COGs which have been experimentally obtained.

Mass Determination by Direct Measurement of Electron Scattering

1975 ◽  
Vol 33 ◽  
pp. 240-241
Author(s):  
M. K. Lamvik ◽  
A. V. Crewe
Keyword(s):  
Cross Section ◽  
Electron Scattering ◽  
Mass Density ◽  
Variable Mass ◽  
Scattering Cross Section ◽  
Mass Determination ◽  
Number Density ◽  
Cross Sectional ◽  
Thin Slice ◽  
Scattering Cross

If a molecule or atom of material has molecular weight A, the number density of such units is given by n=Nρ/A, where N is Avogadro's number and ρ is the mass density of the material. The amount of scattering from each unit can be written by assigning an imaginary cross-sectional area σ to each unit. If the current I0 is incident on a thin slice of material of thickness z and the current I remains unscattered, then the scattering cross-section σ is defined by I=IOnσz. For a specimen that is not thin, the definition must be applied to each imaginary thin slice and the result I/I0 =exp(-nσz) is obtained by integrating over the whole thickness. It is useful to separate the variable mass-thickness w=ρz from the other factors to yield I/I0 =exp(-sw), where s=Nσ/A is the scattering cross-section per unit mass.

Fatality of Suicide Attempts in Amsterdam 1996–2005

Crisis ◽  
2009 ◽  
Vol 30 (4) ◽  
pp. 180-185 ◽  
Author(s):  
Evertjan Jansen ◽  
Marcel C.A. Buster ◽  
Annemarie L. Zuur ◽  
Cees Das
Keyword(s):  
Health Service ◽  
Time Trends ◽  
Suicide Attempts ◽  
Preventive Measures ◽  
Case Fatality ◽  
Absolute Number ◽  
Demographic Differences ◽  
Demographic Groups ◽  
Wish To Die ◽  
Municipal Health

Background: According to recent figures, Amsterdam is the municipality with the highest absolute number of suicides and the second highest suicide rate in the Netherlands. Aims: The aim of the study was to identify time trends and demographic differences in the occurrence of nonfatal suicide attempts versus suicides. Methods: We used registrations of forensic physicians and ambulance services of the Municipal Health Service of Amsterdam to study 1,004 suicides and 6,166 nonfatal attempts occurring in Amsterdam over the period 1996–2005. Results: The number of nonfatal attempts declined from 1996 to 2005, but the number of completed suicides remained relatively stable. Although case fatality was strongly associated with method used, we also found higher case fatalities for men and older people independent of method. Conclusions: The case fatality results suggest differences in motive among different demographic groups: possibly the wish to die is stronger among men and elderly. This finding had implications for the success to be expected from different preventive measures.

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