New method for studying the interaction between light and matter

Dec 13, 2013
Figure 1: Intense attosecond optical pulses provide a potent tool for studying how light interacts with solids, liquids and gases. Credit: VikaSuh/iStock/Thinkstock

Pulses of light are very useful for probing the inner workings of atoms, molecules and solids. Eiji Takahashi and co‐workers from the RIKEN Center for Advanced Photonics, in collaboration with the Center for Free-Electron Laser Science in Germany, have now created a table-top light source that can generate attosecond optical pulses without the complicated level of stabilization required by alternative approaches.

The light source is produced by firing two high-power infrared laser pulses of about 30 femtoseconds—just billionths of a microsecond—in duration into a chamber filled with xenon gas. The mixed infrared light, called a two-color waveform, interacts with the xenon atoms, temporarily releasing electrons. When the electrons return to their host atoms, they produce an isolated extreme-ultraviolet (XUV) pulse (Fig. 1) through a process known as high-harmonic generation. The resultant pulses last just 500 attoseconds, some 60 times shorter than the input pulses. Furthermore, the central wavelength of the pulse is 40 nanometers and its peak energy is 1.3 millijoules—more than a hundred times greater than the energy achieved by previous approaches.

Takahashi's team demonstrated the utility of their light source by applying it to an analytical tool called pump–probe spectroscopy. In this powerful technique, a laser pulse—the pump—strikes an atom and excites its electrons. A second pulse then probes the state of the target at a later time. A full time-dependent picture of the atom and its electron's reaction to the high-power laser light can then be constructed by varying the delay between the pump and probe pulses. The attosecond light pulses created by Takahashi and his team increase the temporal resolution of pump–probe spectroscopy to a level that enables researchers to gain a deeper understanding of ultrafast processes, such as ionization. "Our next step is to develop such an attosecond-pump/attosecond-probe experiment for observing and controlling electronic processes in atomic and molecular physics," says Takahashi.

The real strength of their novel light source, however, is the increase in peak pulse power. The strength of the interaction between light and matter usually scales linearly with the power of the laser light. The pulses of XUV light created by Takahashi and his team should open the door to investigating more complex effects in the nonlinear regime. "We also hope that it will be possible to extend our scheme to even shorter wavelengths, taking the into the soft x-ray region," says Takahashi.

Explore further: Measuring the duration of energetic electron pulses using laser fields

More information: Takahashi, E. J., Lan, P., Mücke, O. D., Nabekawa, Y. & Midorikawa, K. Attosecond nonlinear optics using gigawatt-scale isolated attosecond pulses. Nature Communications 4, 2691 (2013). dx.doi.org/10.1038/ncomms3691

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alexofsarna
1 / 5 (2) Dec 15, 2013
While it is heartwarming to see these trends in physics, it is still frustrating to observe how little progress has been made in physics in the past half-century along certain lines. Einstein proved mathematically a century ago that all things are various forms of energy, which is pure wave forms. String theory has addressed this to an extent, yet the mental constructs involved in its nomenclature can lead to considerable confusion.

This experiment proves further that atoms are nothing more than a conglomeration of wave forms, which emanate in perfect harmonic geometric intervals from the nucleus, which is an eddy current (aka vortex) in the very fabric of what we primitively call space-time, produced by a parallax or junction of multiple harmonically compatible wave forms in some higher dimension, which is a perfect harmonic of the sum-total of what manifests into what we call the external universe.

All is energy, learn the principles governing wave forms to unlock the mysteries!
TheGhostofOtto1923
3 / 5 (2) Dec 16, 2013
alex your comment reminds me of similar maunderings;
."........"in the expansion cycle or stage of the Universe, all matter and energy grow further and further apart with larger spaces in between the components which make up the Universe as well as on an atomic and possibly subatomic level...after the transition occurs and the contracting cycle begins, polarity changes with possible changes and reversals in Physical Laws, and all components of the Universe are attracted to everything else, which makes all matter and energy come closer together...there is no place for the matter/energy components of the Universe to go and it probably all stays in a closed environment."
-What are the odds that 2 individuals could share such a profound level of stupid? Diminishing to none.
antialias_physorg
5 / 5 (1) Dec 16, 2013
hich emanate in perfect harmonic geometric intervals from the nucleus, which is an eddy current (aka vortex) in the very fabric of what we primitively call space-time, produced by a parallax or junction of multiple harmonically compatible wave forms in some higher dimension,...

Stringing together buzzwords does not one sound intelligent make.
(and if you understood any one of the buzzwords you just used to any depth you would quickly realize that you posted total rubbish)
no fate
1 / 5 (1) Dec 17, 2013
"When the electrons return to their host atoms, they produce an isolated extreme-ultraviolet (XUV) pulse (Fig. 1) through a process known as high-harmonic generation."

This process occurs in all excited particles, with a direct correlation between the harmonic frequency and the wavelength of the photon/s that are released.

"We also hope that it will be possible to extend our scheme to even shorter wavelengths, taking the light source into the soft x-ray region," says Takahashi.

Given the combinations of gases and pulse ranges available, I think this extension will occur in short time.