Space Industry and Business News  
TIME AND SPACE
Controlled electron pulses
by Staff Writers
Nuremberg, Germany (SPX) Dec 02, 2016


View through a lens: a laser beam strikes a nanotip. Image courtesy Dr. Michael Forster.

The discovery of photoemission, the emission of electrons from a material caused by light striking it, was an important element in the history of physics for the development of quantum mechanics. Scientists from the Chair of Laser Physics at Friedrich-Alexander-Universitat Erlangen-Nurnberg (FAU) have successfully measured photoemission from sharp metal needles on a scale never before achieved. The researchers' results have been published in the journal Physical Review Letters.

The discovery of photoemission, the emission of electrons from a material caused by light striking it, was an important element in the history of physics for the development of quantum mechanics. Scientists from the Chair of Laser Physics at FAU have successfully measured photoemission from sharp metal needles on a scale never before achieved. The researchers' results have been published in the current issue of the journal Physical Review Letters.

For this two-colour experiment, as they refer to it, the researchers - Dr. Michael Forster, Timo Paschen, Dr. Michael Kruger and Prof. Dr. Peter Hommelhoff - pumped laser pulses with a duration of approximately a nanosecond through a crystal. The crystal combined two photons from the laser pulse.

In addition to the strong laser pulse being shone on the crystal, another weak pulse of light with a higher frequency was created. Particularly remarkable was the discovery that the new photons exhibited twice the energy of the original photons. In an interferometer, the FAU scientists separated both colours and determined the direction of vibration, intensity and delay of both pulses.

When the laser pulses meet on the tungsten needle, their energy is concentrated at the vertex of its tip. This limits electron emission to the end of the tip. The researchers observed that, under optimal parameters, they could almost perfectly turn on and off electron emission by controlling the delays between laser pulses.

This initially came as a surprise, as light energy (photons) can always be found on the tip; therefore this meant that the relative arrival times of the differently-coloured laser pulses determined whether electrons were or were not emitted.

The researchers came to the idea for this control mechanism by comparing experimental results with calculations by physicists working under Prof. Dr. Joachim Burgdorfer at Technische Universitat Wien. They surmised that the electrons could interact with photons from both pulses for emission. This led to two dominant emission paths, but the delay between pulses determined whether these paths would complement or work against each other; emission was either intensified or suppressed in what is known as quantum path interference.

Sharp metal tips have long been used as nearly-punctual electron sources for highest-resolution electron microscopes. Based on the results of this experiment, the researchers hope to create complex electron pulses in the future which could be significant for time-resolved electron microscopy.

The experimental results are also of interest for basic research into surface coherence, as the surface of nanostructures can be particularly well controlled and the nanotips produce exceptionally clear measurement signals thanks to their small dimensions.

The renowned journal Physical Review Letters has published the results in its current issue as the Editors' Suggestion. This section highlights particularly interesting scientific results for the readers of the weekly journal, providing insight into fields outside the scope of their own research.

Research paper


Comment on this article using your Disqus, Facebook, Google or Twitter login.


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only


.


Related Links
University of Erlangen-Nuremberg
Understanding Time and Space






Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
TIME AND SPACE
An Archimedes' screw for groups of quantum particles
Singapore (SPX) Nov 21, 2016
Anyone who has tried to lead a group of tourists through a busy city knows the problem. How do you keep the group together when they are constantly jostled, held up and distracted by the hubbub around them? It's a problem the designers of quantum computers have to tackle. In some future quantum computers, information will be encoded in the delicate quantum states of groups of particles. Th ... read more


TIME AND SPACE
Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

Understanding the way liquid spreads through paper

Laser-based Navigation Sensor Could Be Standard for Planetary Landing Missions

Inside tiny tubes, water turns solid when it should be boiling

TIME AND SPACE
Intelsat General to provide satellite services to RiteNet for US Army network

NSA gives Type1 certification to Harris radio

Upgraded telecommunications network for Marines

Unfurlable mesh reflectors deploy on 5th MUOS satellite

TIME AND SPACE
Russia to face strong competition from China in space launch market

Vega And Gokturk-1A are present for next Arianespace lightweight mission

Antares Rides Again

Four Galileo satellites are "topped off" for Arianespace's milestone Ariane 5 launch from the Spaceport

TIME AND SPACE
High-Precision System for Real-Time Navigation Data of GLONASS Ready for Service

Launch of new Galileo navigation quartet

How NASA and John Deere Helped Tractors Drive Themselves

Flying the fantastic four

TIME AND SPACE
Blues skies thinking to improve aircraft safety

Bolivia may purchase Brazilian Super Tucanos

Kuwait to buy 28 F-18 warplanes: official

Israel orders more F-35 warplanes from US

TIME AND SPACE
For wearable electronic devices, NIST shows plastic holes are golden

Spray-printed crystals to move forward organic electronic applications

Making spintronic neurons sing in unison

World's fastest quantum simulator operating at the atomic level

TIME AND SPACE
NASA Selects Launch Services for Global Surface Water Survey Mission

Early warning from space of homes on the slide

Major space cooperation agreement signed by Italy-Japan Business Group

NASA launches Advanced Geostationary Weather Satellite for NOAA

TIME AND SPACE
New grasses neutralize toxic pollution from bombs, explosives, and munitions

Greenpeace urges microbead ban to protect ocean life

Europe air pollution causes 467,000 early deaths a year: report

Canada pressed to make clean environment a constitutional right









The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.