Featured Research

from universities, journals, and other organizations

Ionization by strong laser fields: Understanding the 'Ionization Surprise'

Date:
February 4, 2011
Source:
Forschungsverbund Berlin e.V. (FVB)
Summary:
In 2009 researchers found an "ionization surprise" that defied explanation. Until that time, it had been commonly thought that the ionization of atoms by strong laser fields was well-understood, but novel experiments where rare gas atoms were ionized using relatively long (few-micrometers) wavelength laser light suddenly revealed an unexpected and universal low-energy feature that defied explanation. Now, scientists have provided an explanation.

In 2009 the journal Nature Physics described an "ionization surprise." Until that time, it had been commonly thought that the ionization of atoms by strong laser fields was well-understood, but novel experiments where rare gas atoms were ionized using relatively long (few-micrometers) wavelength laser light suddenly revealed an unexpected and universal low-energy feature that defied explanation. In this week´s issue of Physical Review Letters, scientists from the University of Rostock, the Max-Planck Institut für Kernphysik in Heidelberg and the Max-Born Institute provide an explanation.

Ionization of atoms by strong laser fields plays an important role in today´s ultrafast laser laboratories. It is at the basis of important techniques such as high-harmonic generation, which allows the generation of attosecond (1 as = 10-18 s) laser pulses, and furthermore allows the development of tomographic methods that make it possible to observe ultrafast electronic and atomic movements on the attosecond to few femtosecond (1 fs = 10-15 s) timescale. Theoretical methods for describing strong laser field ionization were already developed a few decades ago. They are commonly based on the so-called "strong-field approximation" (SFA), which argues that after ionization the motion of the ionized electrons is largely determined by the electric field of the ionizing laser, and hardly by the Coulomb force that the electron and the ion left behind exert on each other.

For several decades the strong-field approximation has served scientists well and has allowed them to understand many observations that were experimentally made in connection with the strong field laser ionization. That is to say, until now. In a remarkable paper last year, scientists from the US and Germany reported the observation of a new phenomenon in strong-field laser ionization, namely a very pronounced peak at low energies in the photoelectron kinetic energy distribution, that contained as many as 50% of the emitted photoelectrons. Remarkably, its physical origin could not be identified.

In the new paper, the Rostock, Heidelberg and MBI scientists argue that it is the failure to include the Coulomb attraction between the departing electron and the ion left behind that is at the root of the low energy feature. They developed a novel theoretical description of strong-field ionization process, which in its initial stages mimics the traditional SFA approach, but then switches to calculating trajectories that the electrons follow in the combined Coulomb + laser field. This approach convincingly reproduces the low energy feature, and shows that it is caused by electrons that are pushed back-and-forth by the oscillatory laser field. In this process the electrons are brought into close proximity to the ion, which strongly disturbs the electron orbit, leading to a situation where the electron can just barely escape the attraction of the ion.

The ´Coulomb-corrected´ SFA formalism based on interfering quantum orbits described above, not only solves the mystery of the "Ionization Surprise" but was also instrumental in related work on the appearance of holographic structures in strong-field ionization, which appears in the journal Science in December.


Story Source:

The above story is based on materials provided by Forschungsverbund Berlin e.V. (FVB). Note: Materials may be edited for content and length.


Journal Reference:

  1. Tian-Min Yan, S. Popruzhenko, M. Vrakking, D. Bauer. Low-Energy Structures in Strong Field Ionization Revealed by Quantum Orbits. Physical Review Letters, 2010; 105 (25) DOI: 10.1103/PhysRevLett.105.253002

Cite This Page:

Forschungsverbund Berlin e.V. (FVB). "Ionization by strong laser fields: Understanding the 'Ionization Surprise'." ScienceDaily. ScienceDaily, 4 February 2011. <www.sciencedaily.com/releases/2010/12/101216095021.htm>.
Forschungsverbund Berlin e.V. (FVB). (2011, February 4). Ionization by strong laser fields: Understanding the 'Ionization Surprise'. ScienceDaily. Retrieved October 1, 2014 from www.sciencedaily.com/releases/2010/12/101216095021.htm
Forschungsverbund Berlin e.V. (FVB). "Ionization by strong laser fields: Understanding the 'Ionization Surprise'." ScienceDaily. www.sciencedaily.com/releases/2010/12/101216095021.htm (accessed October 1, 2014).

Share This



More Matter & Energy News

Wednesday, October 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Japan Looks To Faster Future As Bullet Train Turns 50

Japan Looks To Faster Future As Bullet Train Turns 50

Newsy (Oct. 1, 2014) — Japan's bullet train turns 50 Wednesday. Here's a look at how it's changed over half a century — and the changes it's inspired globally. Video provided by Newsy
Powered by NewsLook.com
US Police Put Body Cameras to the Test

US Police Put Body Cameras to the Test

AFP (Oct. 1, 2014) — Police body cameras are gradually being rolled out across the US, with interest surging after the fatal police shooting in August of an unarmed black teenager. Duration: 02:18 Video provided by AFP
Powered by NewsLook.com
Raw: Japan Celebrates 'bullet Train' Anniversary

Raw: Japan Celebrates 'bullet Train' Anniversary

AP (Oct. 1, 2014) — A ceremony marking 50 years since Japan launched its Shinkansen bullet train was held on Wednesday in Tokyo. The latest model can travel from Tokyo to Osaka, a distance of 319 miles, in two hours and 25 minutes. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Robotic Hair Restoration

Robotic Hair Restoration

Ivanhoe (Oct. 1, 2014) — A new robotic procedure is changing the way we transplant hair. The ARTAS robot leaves no linear scarring and provides more natural results. Video provided by Ivanhoe
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins