Annotation of OpenXM_contrib/gnuplot/demo/reflect.fnc, Revision 1.1.1.1
1.1 maekawa 1: #
2: # Model function for Reflectivity evaluation
3: #
4:
5: mu = 1.130469005513490E-001 # (cm-1) @ 17.479 keV
6: t0 = 0.18 # cm
7: tb = 11.417823202820120 * 0.01745329251994 # thetaB (radians)
8: A = mu * t0 / cos(tb)
9: P = (1 + (cos(2.*tb))**2) / 2
10: Fhkl = sqrt(3.536346308456155**2 + (4.58815426260982e-4)**2) * 0.968
11: r0 = 2.81794092e-13 # classical electron radius
12: lambda = 7.09338062818239e-9 # Mo K in cm
13: V = 1.62253546981499e-23
14: P = (1. + (cos(2.*tb))**2) / 2.
15: #
16: # combine constants to avoid exponential overflow on systems with
17: # D floating point format where exponential limits are ca. 10**(+/-38)
18: # r0liV = r0 * lambda / V
19: r0liV = 2.81794092*7.09338062818239/1.62253546981499e-1
20: #
21:
22: W(x) = 1./(sqrt(2.*pi)*eta) * exp( -1. * x**2 / (2.*eta**2) )
23: Y(tc) = tc/sin(tb) * Fhkl * r0liV
24: f(tc)= (tanh(Y(tc)) + abs(cos(2.*tb)) * tanh(abs(Y(tc)*cos(2.*tb)))) / (Y(tc)*(1.+(cos(2.*tb))**2))
25: Q(tc) = (r0*Fhkl/V)**2 * (lambda**3/sin(2.*tb)) * P * f(tc)
26: a(x) = W(x) * Q(tc) / mu
27:
28: #
29:
30: R(x) = sinh(A*a(x)) * exp(-1.*A*(1.+a(x)))
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