Two 6-hour lectures (A, B) will be proposed, each organized and given by a tandem of Lecturers including one experimentalist and one theoretician. Two 3-hour lectures (C,D) will be proposed on two selected topics. The first lecture (A) will be illustrated with an additional 4-hour numerical practical session.

(A) Time-resolved non-linear optical spectroscopy of molecular systems: theory and experiments

By Tomáš Mančal⁽¹⁾ and Donatas Zigmantas⁽²⁾

Non-linear optical spectroscopy is our main tool for obtaining information on electronic/vibronic structure and ultrafast processes in molecular systems. The nature of this methodology enables a unique synergy between the theory and experiment, and in our lectures we will cover both theoretical and experimental aspects of the topic. We will expose the perturbation response function theory of the non-linear spectroscopy technique using density matrix formalism and the diagramatic notation of the double-sided Feynman diagrams (DSFDs). These diagrams provide a common language for the discussions of spectroscopic signals by both experimentalists and theorists in the field. Using elementary open quantum systems theory and the Frenkel exciton model of molecular aggregates, we will construct the theory of the most important time-resolved spectroscopic techniques such as pump-probe and two-dimensional electronic spectroscopy (2DES). From the experimental perspective we will discuss the most common implementations of 2DES, and use of DSFSs to provide interpretation of the signals acquired with the help of this technique. The advantages afforded by polarization control in the experiments will be deliberated. Revealed synergy between theory and experiment will lead to understanding of what information about molecular systems and photoexcited dynamic processes can be obtained. Keywords: Non-linear spectroscopy, Time-resolved spectroscopy, Two-dimensional electronic spectroscopy, molecular aggregates, Frenkel excitons, energy transfer, anisotropy, open quantum systems

Practical session*: Calculating open system dynamics and non-linear spectra with Quantarhei 

By Vladislav Slama

* Participants should bring their own lap-top or team up with another participant. A preliminary online session will be organized to install the minimal required python environment.

(B) Probing the coupling of molecular vibrations and solvent fluctuations to electronic excitations with linear, non-linear and time-resolved spectroscopies

By Jeffrey Cina⁽¹⁾  and David McCamant⁽²⁾

In "A time-dependent perspective on time-resolved molecular spectroscopy” (3h00), Prof. Cina will discuss wavefunction based theoretical methods to model time-resolved laser experiments and how new different theory and experiment can reveal the wavepacket motion of nuclei as molecular structure evolves during an ultrafast laser experiment.  In “Experiments to capture vibronic coupling: Comparing traditional Raman spectroscopy, femtosecond Stimulated Raman Spectroscopy (FSRS) and transient absorption spectroscopy” (3h00), Prof. McCamant will present the experimental perspective of these same time resolved experiments. Practical considerations when designing and implementing laser systems to study molecular vibronic coupling will be addressed, as well as how one might implement experiments to probe the latest theoretical proposals.  Throughout both lectures, spontaneous Raman, femtosecond stimulated Raman, vibrationally coherent transient absorption spectroscopy and various other spectroscopies that are sensitive to both electronic and vibrational dynamics will be considered and contrasted with each other.   Keywords: vibrational coherence, vibronic transitions, Raman spectroscopy, CARS (Coherent Anti-Stokes Spectroscopy), FSRS (Femtosecond Stimulated Raman Spectroscopy), impulsive stimulated Raman, wavepacket interferometry, IVR (intramolecular vibrational relaxation). 

(C) Probing elementary chemical events on the atto- and femto- second timescales with linear, nonlinear and time-resolved x-ray spectroscopies

By Prof.Linda Young

In “Generation and characterization of attosecond x-ray pulses” (1h30) Prof. Young will discuss the basics of accelerator-based x-ray free electron lasers for the production of attosecond x-ray pulses and compare with table-top methods based upon high harmonic generation for experimental studies of chemical dynamics. 

In “Advancing from linear to nonlinear x-ray spectroscopies” (1h30), Prof. Young will discuss how time-resolved x-ray spectroscopic probes, with their inherent elemental, chemical and spin selectivity, can be used to track photoinduced electronic and nuclear dynamics on the attosecond-Ångstrom scale.  

Keywords: x-ray free electron lasers, attosecond transient absorption spectroscopy, stimulated x-ray Raman, x-ray emission, photon correlation.

(D) Recent advances in coherent multidimensional optical spectroscopies of molecules

By Prof. Shaul Mukamel

1- Probing elementary chemical events on the atto- and femtosecond timescales with linear and nonlinear time-resolved spectroscopies (1h30).  keywords: conical intersections, vibronic coherence, time-resolved chirality, x-ray vs electron diffraction, photoisomerization

2- Using quantum light and entangled photons to enhance nonlinear molecular spectroscopy (1h30). keywords: photon coincidence, pathway selectivity, enhanced spectral and temporal resolution, correlation measurements, photon statistics