CONFOCOR
3
Carl Zeiss
Models
ConfoCor 3
60 M60-1-0025
e
02/2010
C. Bunching Terms
Bunching is the phenomenon of a burst of photons during a certain time interval, the duration of which
is determined by photo-physical processes including triplet, blinking, flickering and protonation. These
terms are exponential decay functions. Formally, they look the same, only the exponential decay might be
different.
C.1 Triplet
)
1
(
)
(
t
e
T
T
G
t
t
t
τ
τ
τ
−
⋅
+
−
=
not
normalized
(7a)
)
1
1
(
)
(
t
t
t
T
e
T
G
t
−
⋅
+
=
−
τ
τ
τ
normalized
(7b)
where T
t
is the triplet fraction, that is the number of molecules undergoing triplet states and
τ
t
the triplet
decay time.
T
t
and
τ
t
are fitted parameters.
Triplet is based on an un-allowed intersystem crossing from the excited to the so-called triplet state. This
state lasts for 1 – 5
µ
s. If the electron drops back to the ground state, no photon is emitted and hence
during the triplet state the molecule is in a dark state. Triplet is indicated as a rise in the correlation
amplitude, which is indicated as a deviation from the flattening curve at shorter correlation times. If not
normalized, the triplet fraction contributes to the total number of molecules.
C.2 Blinking
)
1
(
)
(
b
e
T
T
G
b
b
b
τ
τ
τ
−
+
−
=
not
normalized
(7c)
)
1
1
(
)
(
b
b
b
T
e
T
G
b
−
⋅
+
=
−
τ
τ
τ
normalized
(7d)
where T
b
is the blinking fraction, that is the number of molecules in the dimmer state and
τ
b
the blinking
decay time of the dimmer state. Note, if the blinking term is not normalized, the number of blinking
molecules will influence the total number of molecules.
T
b
and
τ
b
are fitted parameters.
