Humans live on a timescale measured by minutes and seconds, whereas atoms and molecules exist on a timescale measured by femtoseconds and attoseconds. A nanosecond is roughly one billionth of a second (1 x 10-9). An attosecond is one billionth of a nanosecond, or a quintillionth of a second (1 x 10-18 seconds). Throughout the 1990s, scientists had no way of measuring on an attosecond timescale and were using a femtosecond timescale to view the movements of atoms. A femtosecond (1 x10-15 seconds) is one quadrillionth of a second, much faster than a nanosecond and only 1,000 times slower than an attosecond, yet enough to make a difference. According to Niels Bohr’s model of the hydrogen atom, electrons take about 150 attoseconds to orbit the nucleus. From a human perspective, a single second in comparison to this electron’s orbital revolution is roughly the same as 200 million years.
In 1954, Manfred Eigen noted chemical reactions that transpired in nanoseconds, introducing the world to a whole new field of chemistry. Prior to Eigen, these reactions were invisible to human observations.
To view atomic and molecular activities requires rapid strobes of laser light beyond the speed of nanoseconds. The overall movement of these atoms can be seen when viewed at femtoseconds; however, to view the activities of the electrons, these pulses need to be short and quick enough to capture attoseconds. Paul Corkum created the first idea of how to measure an attosecond, and the first recorded measurement of an attosecond in 2002 is attributed to a group of scientists in Vienna led by Ferenc Krausz.
The process of viewing electrons on an attosecond timescale requires the rapid, repetitive pulsation of a laser through one of the noble gases, such as neon. This results in the collision of an atom’s nuclei with its electrons, creating attosecond bursts of X-ray energy. These X-ray bursts can then be focused and redirected to create attosecond pulsations. These attosecond pulses can then be turned toward an atom to track the motion of an electron. One such activity that scientists were able to map was that of the Auger process, the rearrangement of an atom’s electrons to fill a gap created by the loss of an inner shell electron. After knocking an inner shell electron out of its orbit around an atom’s nucleus, scientists have been able to view the movements of the electrons to fill in the gap and the resulting expulsion of another electron, the Auger electron.
Despite the advancements made in the studies of attoscience, scientists are still far from discovering the smallest amount of time, known as Planck time (1 x 10-43). Planck time is the amount of time it takes light to travel across the smallest unit of measurement, Planck length. Beyond these measurements, the traditional spacetime continuum and gravity begin to break down and quantum mechanics needs to be taken into consideration.
See also Chemical Reactions; Light, Speed of; Planck Time; Time, Measurements of
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