A previously proposed method for a weak-field, robust laser control of systems exhibiting a complex intramolecular dynamics (as those with a conical intersection) is improved introducing a more efficient strategy for building up the workspace of states which can be prepared with a good degree of robustness. The search for the state that optimizes the target function (including the observable to be maximized and a penalty function to enforce the robustness of the solution) is accomplished in this space. The method is successfully applied to the control of the time-resolved fluorescence of NO2, a prototype of a small molecule with a very complex dynamics due to the X2A'/A2A' conical intersection. It is shown how the method works for selecting the amplitudes and phases of a multicolor field with a common Gaussian envelope (FWHM=100 fs) which maximizes the fluorescence at various time delays after the switching on of the pulse (the carrier frequencies are taken equal to the strongest absorption bands of the molecule). The analysis of the control mechanism points out that it works through the preparation of a localized wave packet in the best available position for the emission. It is argued that the method allows a very good choice of the starting point in the optimization, thereby strongly reducing the possibility to end in poorly performing local maxima and resulting more effective than genetic algorithms, at least for the present case.
Robust control by a multicolor weak laser pulse of the fluorescence of NO2 from the X2A'/A2A' conical intersection
Lami A;Santoro F
2003
Abstract
A previously proposed method for a weak-field, robust laser control of systems exhibiting a complex intramolecular dynamics (as those with a conical intersection) is improved introducing a more efficient strategy for building up the workspace of states which can be prepared with a good degree of robustness. The search for the state that optimizes the target function (including the observable to be maximized and a penalty function to enforce the robustness of the solution) is accomplished in this space. The method is successfully applied to the control of the time-resolved fluorescence of NO2, a prototype of a small molecule with a very complex dynamics due to the X2A'/A2A' conical intersection. It is shown how the method works for selecting the amplitudes and phases of a multicolor field with a common Gaussian envelope (FWHM=100 fs) which maximizes the fluorescence at various time delays after the switching on of the pulse (the carrier frequencies are taken equal to the strongest absorption bands of the molecule). The analysis of the control mechanism points out that it works through the preparation of a localized wave packet in the best available position for the emission. It is argued that the method allows a very good choice of the starting point in the optimization, thereby strongly reducing the possibility to end in poorly performing local maxima and resulting more effective than genetic algorithms, at least for the present case.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
