Posts Tagged ‘motion’

Polarized object detection in crabs: a two-channel system [RESEARCH ARTICLE]

Melanie Ailin Basnak, Veronica Perez-Schuster, Gabriela Hermitte, and Martin Beron de AstradaMany animal species take advantage of polarization vision for vital tasks such as orientation, communication, and contrast enhancement. Previous studies have …

Einstein in four *spatial* dimension

Why many physicists chose to define the universe in terms of the physical properties of a time or space-time dimension instead of four *spatial* dimensions is puzzling because, as was shown in the earlier article "Defining time" Sept 20, 2007 there is no observational evidence supporting it having physical properties.  Gravity and space-time But even […]

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New technique could reveal the sneakiest black holes in the galaxy

While studying the molecular gas around a distant supernova remnant, researchers at Japan’s Keio University have discovered a new way to detected “quiet” black holes – those that don’t generate an accretion disk or which are not strong enough to emit visible radiation. According to Gizmodo and UPI reports, Keio graduate student Masaya Yamada and […]

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Tracking the ultrafast motion of a single molecule by femtosecond orbital imaging

Watching a single molecule move on its intrinsic timescale has been one of the central goals of modern nanoscience, and calls for measurements that combine ultrafast temporal resolution with atomic spatial resolution. Steady-state experiments access the requisite spatial scales, as illustrated by direct imaging of individual molecular orbitals using scanning tunnelling microscopy or the acquisition of tip-enhanced Raman and luminescence spectra with sub-molecular resolution. But tracking the intrinsic dynamics of a single molecule directly in the time domain faces the challenge that interactions with the molecule must be confined to a femtosecond time window. For individual nanoparticles, such ultrafast temporal confinement has been demonstrated by combining scanning tunnelling microscopy with so-called lightwave electronics, which uses the oscillating carrier wave of tailored light pulses to directly manipulate electronic motion on timescales faster even than a single cycle of light. Here we build on ultrafast terahertz scanning tunnelling microscopy to access a state-selective tunnelling regime, where the peak of a terahertz electric-field waveform transiently opens an otherwise forbidden tunnelling channel through a single molecular state. It thereby removes a single electron from an individual pentacene molecule’s highest occupied molecular orbital within a time window shorter than one oscillation cycle of the terahertz wave. We exploit this effect to record approximately 100-femtosecond snapshot images of the orbital structure with sub-ångström spatial resolution, and to reveal, through pump/probe measurements, coherent molecular vibrations at terahertz frequencies directly in the time domain. We anticipate that the combination of lightwave electronics and the atomic resolution of our approach will open the door to visualizing ultrafast photochemistry and the operation of molecular electronics on the single-orbital scale.

UD Guest Post: Dr Eugen S on “Biological memory vs. memory of materials”

UD has a broad and deep pool of readers and occasional contributors from across the world that have a lot to say, things that are well worth pondering. In this case, I am more than happy to host a guest post in which physicist and computer scientist ES (who hails from Russia) argues the thesis: […]

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