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7.5 The Molecule_2state McXtrace Component
Disordered optical-excitable molecule sample.
Identification
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Author: Erik B Knudsen
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Origin: DTU Physics
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Date: October 2012
Description
A sample model for pump probe experiments which models disordered molecules in a volume (rectangular, cylindrical, or spherical). Molecules can be in one of two states (0 and 1). Scattering is either specified through F vs. q scattering curves or as a set of atom positions from which F vs. q is computed. At t=-delta_t, a fraction of the molecules are put in state 1, from which they decay exponentially, with time constant t_relax, into state 0. For t<-delta_t all of the molecules are in the state specified by initial_state. To improve statistics, scattering may be limited to a ”forward” cone with opening angle in [psimin, psimax]. Furthermore, scattering may be restricted to the azimuthal segment between [etamin,etamax].
Example: Molecule_2state( nq=512,state_0_file=”Fe_bpy_GS_DFT.txt”,state_1_file=”Fe_bpy_ES_DFT.txt”,radius=0.01, psimin=0, psimax=15*DEG2RAD, etamin=-1*DEG2RAD,etamax=1*DEG2RAD, t_relax=600e-12, delta_t=100e-9, excitation_yield=0.2)
Input parameters
Parameters in boldface are required; the others are optional.
|
Name |
Unit |
Description |
Default |
|
|
|||
|
delta_t |
s |
Delay between the exciting event t=0. delay is negative, i.e. delta_t>0 means the exciting event happens before t=0. |
100e-9 |
|
excitation_yield |
1 |
Mean fraction of molecules that get excited. |
0.2 |
|
t_relax |
s |
Mean relaxation time (into state 0) of excited molecules. |
100e-9 |
|
initial_state |
0/1 |
Which state is Molecule_2state in for t<delta_t? Useful for modelling something that changes state slowly. |
0 |
|
psimin |
rad |
Minimum scattering angle off the optical axis. |
0 |
|
psimax |
rad |
Maximum scattering angle off the optical axis. |
M_PI_2 |
|
etamin |
rad |
Minimum scattering angle around the optical axis. |
-M_PI |
|
etamax |
rad |
Maximum scattering angle around the optical axis. |
M_PI |
|
radius |
m |
Radius of cylindrical of spherical sample. |
0 |
|
yheight |
m |
Height of rectangular or cylindrical sample. |
0 |
|
xwidth |
m |
Width of rectangular sample. |
0 |
|
zdepth |
m |
Depth (thickness) of rectangular sample. |
0 |
|
concentration |
m |
Concentration or packing factor of sample. |
1 |
|
p_transmit |
m |
Fraction of statistics devoted to sample direct (unscattered) beam. |
0.1 |
|
form_factors |
str |
File from which to read atomic form factors. Defualt amounts to use the one shipped with McXtrace. |
”FormFactors.txt” |
|
state_0_file |
str |
Isotropic scattering factors (parameterized by q), or atom positions are specified for state 0. |
NULL |
|
state_1_file |
str |
Isotropic scattering factors (parameterized by q), or atom positions are specified for state 1. |
NULL |
|
nq |
1 |
Number of q-bins if F is to be computed from atom positions (Debye formalism). |
512 |
|
material_datafile |
str |
Where to read f1 and f2 factors from in order to handle absorption. |
”Be.txt” |
|
q_parametric |
0/1 |
When 0: Assume that datafiles contains atom positions. 1: datafiles contains F vs. q data. |
0 |
|
Emax |
keV |
Maximal energy for which scattering factors are computed. Must be larger than the maximal impinging energy. |
80 |
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Links
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Component source code found in file Molecule_2state.comp.
Excitable time-dependent sample model
Further Documentaion pending
