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SPEX Reference manual (PDF) - SRON

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118 Response matrices<br />

Figure 7.1: Displacement λ k as a function of the number of resolution elements R. A polynomial<br />

approximation is given in the text.<br />

Table 7.6: Coefficients for the approximations for λ k and c α<br />

i a i b i<br />

0 0.1342 1.3596<br />

1 -0.3388 4.0609<br />

2 0.7994 -4.3522<br />

3 -1.1697 5.2225<br />

4 0.9053 -3.7881<br />

5 -0.2811 1.1491<br />

7.3.8 Examples<br />

Let us apply the theory derived before to some specific line spread functions. First we consider a Cauchy<br />

(or Lorentz) distribution, given by<br />

f(x) =<br />

a<br />

π(a 2 +x 2 ) , (7.30)<br />

where a is the width parameter. The FWHM equals 2a. Next we consider the Gaussian distribution,<br />

given by<br />

f(x) = 1 √<br />

2πσ<br />

e −x2 /2σ 2 , (7.31)

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