This page (revision-12) was last changed on 07-Dec-2016 14:14 by David R Williams

This page was created on 09-Jul-2007 12:35 by JianSun

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Page revision history

Version Date Modified Size Author Changes ... Change note
12 07-Dec-2016 14:14 2 KB David R Williams to previous Took out the discussion about FWHM versus natural width because it was confusing. Result now summarised.
11 22-Jan-2009 05:36 4 KB David R Williams to previous | to last Reply to comment by Celine Boutry, and correction to the description of the instrumental width.
10 21-Jan-2009 15:12 3 KB CelineBoutry to previous | to last
9 21-Jan-2009 09:00 2 KB David R Williams to previous | to last
8 21-Jan-2009 09:00 2 KB David R Williams to previous | to last
7 21-Jan-2009 08:59 2 KB David R Williams to previous | to last
6 21-Jan-2009 08:58 2 KB David R Williams to previous | to last Response to Celine Boutry's question about the instrumental width.
5 21-Jan-2009 08:47 2 KB David R Williams to previous | to last
4 16-Jan-2009 15:36 1 KB CelineBoutry to previous | to last instrumental width
3 09-Jul-2007 13:00 955 bytes Louise Harra to previous | to last
2 09-Jul-2007 12:36 1 KB JianSun to previous | to last
1 09-Jul-2007 12:35 1 KB JianSun to last

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InstrumentalWidthOfEIS...nobody
InstrumentalWidthOfEIS

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[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
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The Doschek ''et al.'' article states a single number, but that is based on comparisons with older data. However, it is still consistent with the numbers derived from comparing the pre-launch laboratory EIS calibration data with the on-orbit EIS data by Brown ''et al.'' (2008). The Brown ''et al.'' numbers are inferred widths, but the reasoning is pretty logical; the fact that the Doschek ''et al.'' (2007) number falls within that range of 0.054nbsp;— 0.057nbsp;Å is comforting.
The Doschek ''et al.'' article states a single number, but that is based on comparisons with older data. However, it is still consistent with the numbers derived from comparing the pre-launch laboratory EIS calibration data with the on-orbit EIS data by Brown ''et al.'' (2008). The Brown ''et al.'' numbers are inferred widths, but the reasoning is pretty logical; the fact that the Doschek ''et al.'' (2007) number falls within that range of 0.054 — 0.057 Å is comforting.
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__NOTE!__ However, the instrumental width that is discussed by Brown ''et al.'' is __not__ the FWHM of the instrumental width, but rather the (1/e)%%sup -1/2%% half-width σ that naturally falls out of the Gaussian function:
__NOTE!__ As Céline Boutry points out, this is the FWHM of the instrumental width (not the Gaussian width σ as previously incorrectly stated here).
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G(x) = exp ( -x%%sup 2%% / 2 (σ%%sup 2%%) )
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The Gaussian width σ is related to the FWHM by the relation:
FWHM = 2 × (2 ln(2) )%%sup 1/2%% × σ
''i.e.,''
FWHM = 2.356 σ
I hope this helps. And please let me know if I've slipped up in my maths!
--[Dave Williams|DavidRWilliams], 21-Jan-2009
--[Dave Williams|DavidRWilliams], 17-Jan-2009
This page (revision-12) was last changed on 07-Dec-2016 14:14 by David R WilliamsTop