Femtosecond real-time observation of wave packet oscillations (resonance) in dissociation reactions

Rose, Todd S.; Rosker, Mark J.; Zewail, Ahmed H.

doi:10.1063/1.454408

Cited by 411 publications

(241 citation statements)

References 28 publications

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“…The wave packet propagation is expected to be only weakly perturbed. The highly quantum nature of superfluid 4 He droplets vs. normal fluid 3 He droplets may affect the coupling of the wave packet motion to the droplet. Moreover, exotic high-spin molecules and complexes formed on He droplets have been studied in real time [31][32][33][34][35][36] .…”

Section: Introductionmentioning

confidence: 99%

Wave Packet Dynamics in Triplet States of Na₂ Attached to Helium Nanodroplets

et al. 2007

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The dynamics of vibrational wave packets excited in Na 2 dimers in the triplet ground and excited states is investigated by means of helium nanodroplet isolation (HENDI) combined with femtosecond pumpprobe spectroscopy. Different pathways in the employed resonant multi-photon ionization scheme are identified. Within the precision of the method, the wave packet dynamics appears to be unperturbed by the helium droplet environment.

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Section: Introductionmentioning

confidence: 99%

Wave Packet Dynamics in Triplet States of Na₂ Attached to Helium Nanodroplets

et al. 2007

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“…An example of the dissipative evolution of a prepared set of states is the study of femtosecond dynamics of dissociation of sodium-iodide molecules by Zewail and coworkers (Engel et al 1988;Rose et al 1988;Zewail, 1988Zewail, , 1990: during the cycle of a vibration of the molecule after being excited to its first excited state by a femtosecond pulse, the passage of the Landau-Zener crossing point (at inter-nuclear separation 6·93 Å) could occur either when the covalent quantum wave packet is on its way out (then leading to dissociation into Na and I atoms) or the ionic wave packet on its way in (leading to trapping of NaI in the bound ground state). Whereas, a single-particle experiment would encounter a problem to resolve the wave packet motion because of the uncertainty principle, the quantum statistics of the large number of molecules coherently excited by a femtosecond pulse, to vibrate all of them in phase, will over-rule the uncertainty and provide macroscopic features to the oscillations, possible to experimentally follow as either activated complex or free atoms, appearing as ringing (resonance) particle emission intensities with coinciding temporal peak positions.…”

Section: How Einstein (Possibly) Was Thinkingmentioning

confidence: 99%

Quantum entanglement: facts and fiction – how wrong was Einstein after all?

Nordén

2016

Quart. Rev. Biophys.

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Abstract. Einstein was wrong with his 1927 Solvay Conference claim that quantum mechanics is incomplete and incapable of describing diffraction of single particles. However, the Einstein-Podolsky-Rosen paradox of entangled pairs of particles remains lurking with its 'spooky action at a distance'. In molecules quantum entanglement can be viewed as basis of both chemical bonding and excitonic states. The latter are important in many biophysical contexts and involve coupling between subsystems in which virtual excitations lead to eigenstates of the total Hamiltonian, but not for the separate subsystems. The author questions whether atomic or photonic systems may be probed to prove that particles or photons may stay entangled over large distances and display the immediate communication with each other that so concerned Einstein. A dissociating hydrogen molecule is taken as a model of a zero-spin entangled system whose angular momenta are in principle possible to probe for this purpose. In practice, however, spins randomize as a result of interactions with surrounding fields and matter. Similarly, no experiment seems yet to provide unambiguous evidence of remaining entanglement between single photons at large separations in absence of mutual interaction, or about immediate (superluminal) communication. This forces us to reflect again on what Einstein really had in mind with the paradox, viz. a probabilistic interpretation of a wave function for an ensemble of identically prepared states, rather than as a statement about single particles. Such a prepared state of many particles would lack properties of quantum entanglement that make it so special, including the uncertainty upon which safe quantum communication is assumed to rest. An example is Zewail's experiment showing visible resonance in the dissociation of a coherently vibrating ensemble of NaI molecules apparently violating the uncertainty principle. Einstein was wrong about diffracting single photons where space-like anti-bunching observations have proven recently their non-local character and how observation in one point can remotely affect the outcome in other points. By contrast, long range photon entanglement with immediate, superluminal response is still an elusive, possibly partly misunderstood issue. The author proposes that photons may entangle over large distances only if some interaction exists via fields that cannot propagate faster than the speed of light. An experiment to settle this 'interaction hypothesis' is suggested.In 1935, Einstein, Podolsky and Rosen (EPR) presented a paradox, which seemed to imply a fundamental discrepancy between quantum and classical mechanics and which they meant proves that the former is not a 'complete theory' . Einstein (1936) elaborated on the theme with a more nuanced description later, in what sense he considers quantum mechanics (QM) incomplete. His concern that it is the way QM is applied to singular particulate systems rather than whether it is a correct theory, was my inspiration for revisiting these grounds a...

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“…Femto-chemistry can help to find out (i) whether or not the atomic dissociation limit is a scaled form of the ionic asymptote, which seems unlikely but can not be excluded or (ii) if crossing of ionic and atomic states is really avoided. As in the case of NaI (Rose et al, 1988), femto-chemistry can be of assistance to verify which species are present in this critical region of covalent molecules X 2 like Li 2 . If ions Li -and Li + are found experimentally, this would be conclusive evidence in favour of an electrostatic approximation to chemical bonding.…”

Section: Decisive Experimental Evidencementioning

confidence: 99%