Controlling Quantum Interferences in IR Vibrational Excitations in Metal Carbonyls

Abstract

Abstract.Coherent controls over vibrational excitations in metal di-carbonyls were demonstrated by using phase-shaped mid-infrared pulses. The phase of the inter-state coherence between two different normal-modes was controlled by changing the phase step of the stepwise spectral phase profile. The quantum interference between multiple vibrational excitation paths in resonant two-step excitations was manipulated by the similar spectral phase control. The results experimentally confirmed that coherent control over multiple vibrational degrees of freedom works properly in condensed phases. There remains the possibility for increasing excitation efficiency by introducing group-delays and by optimizing polarization state of the excitation pulse. Motivation and ObjectivesCoherent control is a technique that manipulates interference of wave functions by adjusting their amplitudes and phases. Recent developments in the pulse shaping technique in MIR [1] may open a way toward coherent control over molecular motions/reactions at the electronic ground states. Such control may serve for novel information processing and molecular reaction controls, including bond breakage, structural isomerization, hydrogen bond rearrangement, proton transfer, etc. [2][3][4]. So far the MIR pulse shaping was applied to the ladder climbing of a single vibrational mode [5].The broadband nature of the ultrashort MIR pulses, however, should also be able to excite multiple vibrational modes in a correlated manner to control nuclear motion in multi-dimensional coordinates and to create highly-excited vibrational states. The ability to handle multiple vibrational modes should increase the variety and efficiency of controllable reactions. For such coherent control applications, control over quantum interference as well as efficient ladder climbing is essential. In this paper, we show that the quantum interferences in IR vibrational excitations were successfully controlled for liquid-phase molecules by use of MIR phase-shaping. MIR Pulse Shaping and Transient Absorption SpectroscopyMIR pulses of 100-fs duration and 5-J energy were generated by the OPA/DFG system. Major portion of the pulse energy was delivered to the pulse shaper, consisting of diffraction gratings, concave mirrors and the germanium AOM, developed by Zanni-group [1]. The shaped pulse was characterized by the electric-field cross correlation in the spectral interferometry with a reference EPJ Web of Conferences

Laser-driven localization of collective CO vibrations in metal-carbonyl complexes

“…Of course, when it comes to experimental observation care needs to be taken of the fact that actually a distribution of differently oriented molecules will be excited. Concerning the experimental signatures of the proposed transient localization we note that Ashihara et al [14] in their laser control experiment attributed an oscillatory signal in transient pump-probe spectroscopy to the creation of a coherent superposition between symmetric and antisymmetric fundamental transitions. How the present dynamics reflects in timeresolved nonlinear spectroscopy remains to be investigated.…”

“…An extension, now including polarization shaping, was later shown to be able to discriminate between excitation of different carbonyl-stetching modes in MnBr(CO) 5 [13]. Phase shaping laser control of coherent superposition states corresponding to two different CO vibrations was demonstrated by Ashihara et al for an iridium dicarbonyl complex in solution [14]. Pushing vibrational ladder climbing towards reaction control it was shown experimentally that rather high excitation levels can be reached such as to enable bond breaking mediated by intramolecular vibrational energy redistribution (IVR) [9] or by direct excitation of the reaction coordinate [10].…”