# 2D SFCS CC
# 2D on component correlation function for perpendiculat SFCS.
# Model function for PyCorrFit.
# http://fcstools.dyndns.org/pycorrfit/
# http://fcstools.dyndns.org/pyscanfcs/
# The detection profile is eliptical, as the focus passes the membrane
# perpendicular to its axis of symmetry.
# The axis ratio / strucure parameter is defined as:
# SP = semi-major-axis / semi-minor-axis (wz/w0)
# This model describes the cross-correlation for two-focus FCS

## Parameters
# Number of particles
Nob = 40.0
# Diffusion time
taudiff [ms] = 1.0
# axis ratio / structural parameter
SP = 5
# Beam waist radius
w0 [100nm] = 2.3
# Distance between the foci
d [100nm] = 5.0

gFirst = 1/sqrt(1+tau/taudiff)
gSecond = 1/sqrt(1+tau/(taudiff*SP**2))

gac = 1/Nob * gFirst * gSecond
# Diffusion coefficient:
gD = w0**2/(4*taudiff)
gcc = exp(-d**2/(w0**2+4*gD*tau))

G = gac*gcc
