function [a_phi] = aphi(wavelength, Sf)
%This function computes a_phi based on the data of Aurea M 2002
wl = 400:2:650;
a_pico = [1.682
1.734
1.8
1.89
1.978
2.057
2.162
2.269
2.327
2.398
2.457
2.533
2.614
2.663
2.749
2.804
2.84
2.915
2.947
2.978
3.014
3.032
3.011
2.965
2.937
2.888
2.816
2.783
2.706
2.655
2.59
2.526
2.455
2.402
2.331
2.281
2.205
2.136
2.063
2.049
1.998
1.93
1.918
1.897
1.867
1.812
1.776
1.701
1.648
1.522
1.439
1.373
1.27
1.162
1.04
0.961
0.886
0.794
0.734
0.665
0.617
0.544
0.522
0.486
0.448
0.391
0.375
0.336
0.305
0.292
0.288
0.261
0.245
0.214
0.194
0.187
0.138
0.137
0.111
0.094
0.095
0.07
0.053
0.076
0.064
0.043
0.05
0.051
0.065
0.067
0.084
0.111
0.072
0.073
0.073
0.099
0.07
0.095
0.085
0.09
0.086
0.068
0.078
0.069
0.09
0.096
0.094
0.084
0.105
0.128
0.119
0.126
0.138
0.146
0.135
0.175
0.189
0.176
0.203
0.19
0.19
0.191
0.174
0.197
0.176
0.168];
a_micro = [1.574
1.584
1.6
1.617
1.633
1.654
1.669
1.674
1.684
1.697
1.708
1.71
1.716
1.737
1.763
1.793
1.812
1.827
1.83
1.834
1.824
1.8
1.771
1.741
1.712
1.685
1.667
1.65
1.641
1.631
1.631
1.623
1.616
1.606
1.592
1.568
1.542
1.509
1.481
1.459
1.437
1.415
1.399
1.387
1.377
1.367
1.349
1.338
1.319
1.301
1.271
1.242
1.222
1.196
1.169
1.141
1.118
1.096
1.075
1.057
1.035
1.013
0.992
0.977
0.959
0.944
0.927
0.909
0.888
0.868
0.847
0.826
0.806
0.785
0.764
0.737
0.711
0.682
0.653
0.626
0.604
0.58
0.555
0.535
0.514
0.501
0.487
0.478
0.475
0.468
0.464
0.459
0.452
0.452
0.449
0.443
0.433
0.424
0.416
0.406
0.401
0.4
0.403
0.408
0.416
0.429
0.443
0.458
0.473
0.487
0.495
0.499
0.504
0.514
0.521
0.525
0.532
0.535
0.534
0.535
0.532
0.528
0.526
0.528
0.538
0.549];
a_pico = interp1(wl,a_pico,wavelength,'linear');
a_micro = interp1(wl,a_micro,wavelength,'linear');
aphi = Sf*a_pico + (1-Sf)*a_micro;
a_phi = interp1(wavelength,aphi,wavelength,'linear');