Fourier transform coherent control

Cowley 1981) ( is a convolution integral and FT is the Fourier transform). The phase-contrast imaging performance of an HRTEM is controlled by sin x, which contains the basic phase-contrast sinusoidal terms modified by an attenuating envelope function, F 9), which is essentially due to the partial coherence of the electron beam ... 

We have developed ultrahigh-precision coherent control based on this WPI, in which we have succeeded in visualizing and controlling the ultrafast evolution of a WP interference in a molecule with precisions on the picometer spatial and attosec-ond (as) temporal scales [37-39], This is the cutting edge of coherent control. We have utilized this ultrahigh-precision coherent control to develop a molecular computer that executes ultrafast Fourier transform with molecular wave functions in 145 fs [40,41], More recently, we have extended the target of our coherent control to wave functions delocalized in a bulk solid [42,43], In this account, we will describe these developments of our experimental toolbox and the outlook toward the coherent control around the quantum-classical boundary. 

Finally, coherent transfer of population between electronic states was demonstrated using intense ultrashort laser pulses of different durations. Aided by calculations, it was shown that the population in various neutral electronic states of both Na2 and Na3 at the end of the interaction with a laser pulse can be controlled by varying the laser intensity. A second (intense) probe laser was used to ionize the molecules. The Fourier transform obtained from the transient ion signal can be used to experimentally monitor the population distribution created by the first laser pulse. 

The systematically performed pump-probe spectroscopy on alkali clusters provided a good indication about suited candidates for a coherent control experiment. Among these, the fragmentation dynamics of the heteronu-clear trimer Na2K appeared to us the best. The corresponding pump-probe spectrum is shown in Fig. 14(a). It clearly exhibits — superimposed on an exponential decay with a time constant of 3.28 ps — an oscillatory behaviour with a period of roughly 500 fs. The Fourier-transform of this... 

This temporal coherent control technique allows the extraction of detailed information on the structure of the excited molecular states with a precision similar to that of high resolution Fourier transform spectroscopy. It provides an efficient way of controlling the creation of a wave packet in a bound state. A simultaneous excitation of two or even more excited states may enable... 

It is not in the scope of the present chapter to review all possible experimental setups for the various types of Raman scattering classical, microprobe, Fourier transform (FT), coherent anti-Stokes (CARS), surface enhanced (SERS), hyper (HRS), photo-acoustic (PARS), and so forth (see, e.g.. Refs. 29-31). A basic Raman-scattering instrument requires a laser-light source, an appropriate sample holder, a sample illumination optical unit, a scattered-light collection optical unit (these two may be combined in one system), a disperser (spectrometer) or an interferometer, a light detection unit, a recorder, and an appropriate microcomputer able to drive, control, and record all of the experimental parameters as well as the results and their processing. 

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