Horn
12th September 2012, 04:52 PM
Moved from the LDS thread...
Chronometry with an ingenious experiment
The fact that the physicists can now look in more detail at photoemission is attributable to attosecond spectroscopy: "It is only recently that we have been able to observe processes that last only a few billionths of a billionth of a second," says Ferenc Krausz. However, even the extremely short laser pulses do not constitute a stopwatch with which the absolute starting time of an electron after the arrival of a laser pulse can be measured. "Instead, our experiments give a very reliable indication, so that we are able to deduce the delay and estimate its duration," explains Martin Schultze.
He and his colleagues have measured the time difference with which electrons start from different orbitals. An orbital describes the space in which an electron is located, and also determines the reaction of an electron to the laser bombardment. And just as different sprinters differ in how well they fly off the starting blocks, the electrons also do not fly out of different orbitals with the same delay. The physicists apply a clever trick to measure the difference between their starting times.
Their test object is a cloud of the noble gas neon and they focus their sights on electrons from two orbitals. They now chase the pulse of very energetic ultraviolet light onto the atoms, a pulse which flashes for only a few tens of attoseconds and knocks different electrons out of the noble gas particle. Moreover, they also beam an infrared laser pulse, which last around 40 times longer than the ultraviolet flash, onto the atoms. They synchronize both pulses such that the shorter ultraviolet one always impinges on the atoms when the longer infrared laser wave is already there.
http://1.rp-api.com/1697028/via.pngredOrbit (http://s.tt/1auJB) (http://s.tt/1auJB)
Chronometry with an ingenious experiment
The fact that the physicists can now look in more detail at photoemission is attributable to attosecond spectroscopy: "It is only recently that we have been able to observe processes that last only a few billionths of a billionth of a second," says Ferenc Krausz. However, even the extremely short laser pulses do not constitute a stopwatch with which the absolute starting time of an electron after the arrival of a laser pulse can be measured. "Instead, our experiments give a very reliable indication, so that we are able to deduce the delay and estimate its duration," explains Martin Schultze.
He and his colleagues have measured the time difference with which electrons start from different orbitals. An orbital describes the space in which an electron is located, and also determines the reaction of an electron to the laser bombardment. And just as different sprinters differ in how well they fly off the starting blocks, the electrons also do not fly out of different orbitals with the same delay. The physicists apply a clever trick to measure the difference between their starting times.
Their test object is a cloud of the noble gas neon and they focus their sights on electrons from two orbitals. They now chase the pulse of very energetic ultraviolet light onto the atoms, a pulse which flashes for only a few tens of attoseconds and knocks different electrons out of the noble gas particle. Moreover, they also beam an infrared laser pulse, which last around 40 times longer than the ultraviolet flash, onto the atoms. They synchronize both pulses such that the shorter ultraviolet one always impinges on the atoms when the longer infrared laser wave is already there.
http://1.rp-api.com/1697028/via.pngredOrbit (http://s.tt/1auJB) (http://s.tt/1auJB)