Posts Tagged ‘attoseconds’
Lasers that Flash in a Quintillionth of a Second Could ‘Film’ Electrons as they Interact
Capturing electrons on “film” isn’t easy--imagine the shutter speed you would need to capture something moving so fast that it can rotate a central hub in 151 billionths of a billionth of a second. That’s how fast the electron orbiting a hydrogen nucleus is moving, so in order to capture it in the act you need something with attosecond resolution. In other words, you need a laser capable of pulsing at the attosecond scale.
Attosecond laser pulses have been demonstrated before, but they were too weak to actually measure electron dynamics. For that, you need something both fast and intense. This new laser system satisfies both requirements, and does so with a relatively simple setup.
To get super-short bursts of laser light, you need to combine light waves of different frequencies in a very precise way such that they reinforce each other. This is easier said then done, particularly because it’s hard to get two different laser beams synchronized precisely. To overcome this, the researchers constructed a setup that runs a single laser beam through a beam splitter, producing two beams of different frequencies that are nonetheless the same beam. And because they share the same origin, they remain in sync.
But they’re still not at the attosecond level yet. Several other things have to happen to reach the proper intensities and durations necessary for attosecond-scale measurements. But a paper the team recently published in Nature Photonics outlines the road to attosecond resolutions in such a way that other researchers think its only a matter of time (and, more specifically, a matter of amplification) before we’re looking at individual electrons in a way in which we’ve never seen them before.
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German Scientists Measure How Fast an Electron Jumps, the Shortest Time Interval Ever Measured
During photoemission – the expulsion of electrons from an atom by bombarding them with high-energy light – it’s always been assumed that there is no delay between the photons’ impact and the breaking loose of the target electron. But a group of German researchers in collaboration with Greek, Austrian, and Saudi Arabian colleagues decided to challenge that assumption with extremely sensitive time measurement tech.
The team bombarded atoms of neon gas with near-infrared laser light in 10-15 second pulses and ultraviolet pulses of far shorter durations of just 180 attoseconds (remember, an attosecond is one billionth of one billionth of one second). The near-IR light served as an attosecond chronograph, measuring the time of UV impact and the time the electrons exited their orbits.
Their findings turned up two interesting results. For one, they found that electron ejection is not a “time zero” action as once presumed, but that excited electrons hesitate very, very briefly before leaving the atom. But perhaps more interesting, they found that electrons from different orbitals behaved differently, leaving the atom at slightly different times even though they were impacted simultaneously.
The researchers are not exactly sure why this is, but it likely has to do with some small, overlooked influence that electrons exert over one another that is different that the forces exerted on electrons by their nuclei. If that’s the case, the tiny time lag could have big consequences for physics, a discipline ruled by the interactions between atoms and the behavior of electrons. Until they figure all that out, they can at least take pride in their 20-attosecond record for the shortest time interval ever directly measured.
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