COHERENTNONLINEARSPECTROSCOPY: From Femtosecond Dynamics to Control

Abstract

This review focuses on the study of the dynamics of isolated molecules and their control using coherent nonlinear spectroscopic methods. Emphasis is placed on topics such as bound-to-free excitation and the study of concerted elimination reactions, free-to-bound excitation and the study of bimolecular reactions, and bound-to-bound excitation and the study of intramolecular rovibrational dynamics and coherence relaxation. For each case the detailed time-resolved information reveals possible strategies to control the outcome. Experimental results are shown for each of the reactions discussed. The methods discussed include pump-probe and four-wave mixing processes such as transient grating and photon echo spectroscopy. Off-resonance transient-grating experiments are shown to be ideal for the study of ground state dynamics, molecular structure, and the molecular response to strong field excitation.

The conformational stability of gaseous 1-butene studied by femtosecond nonlinear spectroscopy and ab initio calculations

“…Based on the Raman process, this technique has proven to be a powerful tool for structural investigation of molecules and molecular clusters in the electronically ground state even if they do not possess a permanent dipole moment [11][12][13][14]. Recently, fs DFWM was successfully applied for studying large amplitude intramolecular motions in the non-aromatic five-membered ring compounds pyrrolidine [15] and cyclopentene [16].…”

Ultrafast Laser Induced Molecular Alignment and Deformation: Experimental Evidence from Neutral Molecules and from Fragment Ions

“…Because only a portion of the population is bent (the 35% value arises from the fact that 72% of the intensity of a Gaussian pulse is contained in the central part of the beam), the rotational revival from all the molecules in the sample needs to be added and then squared to obtain the observed heterodyne detected signal. 37,40 When we add 35% of bent molecules, we see changes in the resulting signal, as shown in Figure 11b-f. The simulation in Figure 11e fits our data closely, while the simulations in Figure 11d and f do not.…”

“…This setup was used to make our first observations of alignment and structural deformation following intense off-resonance excitation. [38][39][40] The presentation is organized as follows. We present briefly the laser systems and experimental setups used for our measurements.…”

MARC Data Collection- A Flawed Process

“…The work of Zewail's group [15,16] was based on pump-probe techniques where they prepared an excited state with a pump beam and detected the laserinduced fluorescence signal when excited by a delayed probed beam; this is similar to the fs-CARS technique, where the molecular coherence is prepared by the overlapping pump and Stokes beam and is then probed by a delayed probe beam. The review paper by Dantus [17] provides a comprehensive discussion of the coherent nonlinear spectroscopy based on ultrafast lasers.…”