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either changing the height of the potential barrier or the depth of the potential well,
which alter the level position. In Fig.
3.13
the depth of the potential well is
determined by the charge of the nitrogen atom N
+
. Out of four control groups in
two—the first and the third, the charge on N
+
does not change. At the same time for
the second and the fourth control groups, a restructuring accompanied by a change
of the charge on the nitrogen atom is possible which may be caused, for example, by
the absorption of light by one of the molecular groups at the entry point, as shown in
the figure (compare entry points
B
and
D
). Since neutralization of the aromatic
group leads to substantial change in the shape and location of the well as well as in
the position of energy levels within it, free passage of the electron will be impos-
sible and the transmission coefficient of the system will decrease sharply. Using
molecular fragments of different structures as control groups, one can ensure that
structure rearrangement of the device will occur at different photon energies at
different entry points. Such molecular element operates using optical information
input. There may be other ways of influencing control groups, such that an electron
enters the input, or a structure rearrangement caused by the proliferation of charged
solitons takes place.
The molecular NOR element proposed by Carter, and acting on the same
principles, is shown in Fig.
3.14
. It is a stack of molecules which are gallium
