Manifestations of classical physics in the quantum evolution of correlated spin states in pulsed NMR experiments

Multiple-pulse NMR experiments are a powerful tool for the investigation of mole- cules with coupled nuclear spins. The product operator formalism provides a way to understand the quantum evolution of an ensemble of weakly coupled spins in such experiments using some of the more intuitive concepts of classical physics and semi- classical vector representations. In this paper I present a new way in which to inter- pret the quantum evolution of an ensemble of spins. I recast the quantum problem in terms of mixtures of pure states of two spins whose expectation values evolve identi- cally to those of classical moments. Pictorial representations of these classically evolving states provide a way to calculate the time evolution of ensembles of weakly coupled spins without the full machinery of quantum mechanics, offering insight to anyone who understands precession of magnetic moments in magnetic fields

Manifestation of classical wave delays in a fully quantized model of the scattering of a single photon

We consider a fully quantized model of spontaneous emission, scattering, and absorption, and study propagation of a single photon from an emitting atom to a detector atom both with and without an intervening scatterer. We find an exact quantum analog to the classical complex analytic signal of an electromagnetic wave scattered by a medium of charged oscillators. This quantum signal exhibits classical phase delays. We define a time of detection which, in the appropriate limits, exactly matches the predictions of a classically defined delay for light propagating through a medium of charged oscillators. The fully quantized model provides a simple, unambiguous, and causal interpretation of delays that seemingly imply speeds greater than c in the region of anomalous dispersion.Comment: 18 pages, 4 figures, revised for clarity, typos corrrecte

Atomic Resonance and Scattering

Contains reports on eight research projects.National Science Foundation (Grant PHY83-06273)National Bureau of Standards (Grant NB83-NAHA-4058)National Science Foundation (Grant PHY84-11483)Joint Services Electronics Program (Contract DAAG29-83-K-0003)U.S. Navy - Office of Naval Research (Contract NO0014-79-C-0183)U.S. Navy - Office of Naval Research (Contract N00014-83-K-0695)National Science Foundation (Grant PHY83-07172-A01

Atomic Resonance and Scattering

Contains reports on nine research projects.National Science Foundation (Grant PHY79-09743)National Science Foundation (Grant PHY82-10486)Joint Services Electronics Program (Contract DAAG29-83-K-0003)U.S. Navy - Office of Naval Research (Contract N00014-79-C-0183)National Bureau of Standards (Grant NB83-NAHA-4058)National Science Foundation (Grant CHE79-02967-A04)National Science Foundation (Grant PHY83-07172)Joint Services Electronics Program (Grant DAAG29-83-K-0003

Resonant Infrared Multiple Photon Dissociation Spectroscopy of Anionic Nucleotide Monophosphate Clusters

We report mid-infrared spectra and potential energy surfaces of fouranionic, 2′-deoxynucleotide-5′-monophosphates (dNMPs) and the ionic DNA pairs[dGMP-dCMP−H]1−, [dAMP-dTMP−H]1− with a total charge of the complex equal to−1. We recorded IR action spectra by resonant IR multiple-photon dissociation (IRMPD)using the FELIX free electron laser. The potential energy surface study employed an onthe-fly molecular dynamics quenching method (MD/Q), using a semiempirical AM1method, followed by an optimization of the most stable structures using density functionaltheory. By employing infrared multiple-photon dissociation (IRMPD) spectroscopy incombination with high-level computational methods, we aim at a better understanding ofthe hydrogen bonding competition between the phosphate moieties and the nucleobases.We find that, unlike in multimer double stranded DNA structures, the hydrogen bonds inthese isolated nucleotide pairs are predominantly formed between the phosphate groups.This intermolecular interaction appears to exceed the stabilization energy resulting frombase pairing and directs the overall cluster structure and alignment