Journal article
Fundamental Limits of the Dispersion of the Two-Photon Absorption Cross-Section
The Journal of chemical physics, Vol.123(19), pp.194101-194101
08/08/2005
Handle:
https://hdl.handle.net/2376/115728
PMID: 16321070
Abstract
Javier Perez Moreno and Mark G. Kuzyk, J. Chem. Phys. 123, 194101
(2005). (13 pages) We rigorously apply the sum rules to the sum-over-states expression to
calculate the fundamental limits of the dispersion of the two-photon absorption
cross-section. A comparison of the theory with the data suggests that the
truncated sum rules in the three-level model give a reasonable fundamental
limit. Our ansatz that the two photon absorption cross-section near the limit
must have only three dominant statesis is supported by a rigorous analytical
calculation that the resonant term gets smaller as more states are added. We
also find that the contributions of the non-explicitly resonant terms can not
be neglected when analyzing real molecules with many excited states, even near
resonance. However, puzzling as it may be, extrapolating an off-resonant result
to resonance using only the resonant term of the three-level model is shown to
be consistent with the exact result. In addition, the off-resonant
approximation is shown to scale logarithmically when compared with the full
three-level model. This scaling can be used to simplify the analysis of
measurements. We find that existing molecules are still far from the
fundamental limit; so, there is room for improvement. But, reaching the
fundamental limit would require precise control of the energy-level spacing,
independently of the transition dipole moments -- a task that does not appear
possible using today's synthetic approaches. So, we present alternative methods
that can still lead to substantial improvements which only require the control
of the transition moment to the first excited state. While it is best to
normalize measured two photon absorption cross-sections to the fundamental
limits when comparing molecules, we show that simply dividing by the square of
the number of electrons per molecule yields a good metric for comparison.
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Details
- Title
- Fundamental Limits of the Dispersion of the Two-Photon Absorption Cross-Section
- Creators
- Javier Pérez MorenoMark G Kuzyk
- Publication Details
- The Journal of chemical physics, Vol.123(19), pp.194101-194101
- Academic Unit
- Physics and Astronomy, Department of
- Identifiers
- 99900547963101842
- Language
- English
- Resource Type
- Journal article