47 research outputs found
Frequency-Domain Time-Resolved Four Wave Mixing Spectroscopy of Vibrational Coherence Transfer with Single-Color Excitation
On the conductivity in a two-dimensional molecular π-stack with application to charge transport in DNA solid-state devices
Multiresonant Coherent Multidimensional Vibrational Spectroscopy of Aromatic Systems: Pyridine, a Model System
Spectral Isolation and Measurement of Surface-Trapped State Multidimensional Nonlinear Susceptibility in Colloidal Quantum Dots
Multiresonant coherent multidimensional spectroscopy
(CMDS) is
a powerful new method for probing the coupling between vibrational
modes and their dynamics. The line narrowing that occurs because of
the multidimensional nature of CMDS allows the separation of homogeneous
and inhomogeneous broadening and enhances spectral resolution. Recent
work has extended multiresonant CMDS to electronic resonances in quantum
confined nanostructures. Vibrational modes of the solvent also appear
in the CMDS spectra. The phase oscillations of the vibrational and
electronic coherences interfere and change the line shapes. Since
the form of the vibrational third-order susceptibility and hyperpolarizability
are well-known and since they can be measured against known standards,
it becomes possible to use the interference effects as a probe of
the absolute magnitude and phase of the electronic resonances. This
approach is demonstrated using PbSe quantum dots where incomplete
capping causes ultrafast relaxation to a new electronic state that
appears directly in the CMDS spectra. The new state is believed to
be a mixed core/surface exciton. Closed-form expressions for the electronic
nonlinearities are used to analyze the frequency dependence of the
fully resonant complex hyperpolarizability of the 1S exciton and the
surface-trapped state. The ability of mixed frequency/time domain
multiresonant
CMDS methods to spectrally resolve surface states promises to be
an important new way to characterize the interface states in complex
heterostructures and the surface states that define the stability
of nanostructures resulting from different synthetic strategies
Multiply Resonant Coherent Multidimensional Spectroscopy: Implications for Materials Science
Spectral Isolation and Measurement of Surface-Trapped State Multidimensional Nonlinear Susceptibility in Colloidal Quantum Dots
Multiresonant coherent multidimensional spectroscopy
(CMDS) is
a powerful new method for probing the coupling between vibrational
modes and their dynamics. The line narrowing that occurs because of
the multidimensional nature of CMDS allows the separation of homogeneous
and inhomogeneous broadening and enhances spectral resolution. Recent
work has extended multiresonant CMDS to electronic resonances in quantum
confined nanostructures. Vibrational modes of the solvent also appear
in the CMDS spectra. The phase oscillations of the vibrational and
electronic coherences interfere and change the line shapes. Since
the form of the vibrational third-order susceptibility and hyperpolarizability
are well-known and since they can be measured against known standards,
it becomes possible to use the interference effects as a probe of
the absolute magnitude and phase of the electronic resonances. This
approach is demonstrated using PbSe quantum dots where incomplete
capping causes ultrafast relaxation to a new electronic state that
appears directly in the CMDS spectra. The new state is believed to
be a mixed core/surface exciton. Closed-form expressions for the electronic
nonlinearities are used to analyze the frequency dependence of the
fully resonant complex hyperpolarizability of the 1S exciton and the
surface-trapped state. The ability of mixed frequency/time domain
multiresonant
CMDS methods to spectrally resolve surface states promises to be
an important new way to characterize the interface states in complex
heterostructures and the surface states that define the stability
of nanostructures resulting from different synthetic strategies
Multiresonant Coherent Multidimensional Electronic Spectroscopy of Colloidal PbSe Quantum Dots
We demonstrate the use of multiresonant coherent multidimensional spectroscopy (CMDS) for obtaining 2D spectra of the diagonal and cross-peaks of the 1S and 1P excitons and biexcitons in PbSe quantum dots and their coherent and incoherent dynamics. We show that multiresonant CMDS line narrows the inhomogeneous broadening and resolves the excitonic peaks from the background that often obscures peaks. We develop theoretical methods that extract details of the homogeneous and inhomogeneous broadening, the Coulombic coupling within the biexciton, and the relative exciton and biexciton transition moments. The population dynamics are measured by scanning the excitation pulse time delays over all time orderings. Phase modulations of individual coherences are observed because of heterodyning between scattered light and the four-wave mixing signal. The experiments demonstrate that CMDS can be used to obtain quantum state resolved dynamics of the electronic states in complex nanostructures and other important materials