Flash photolysis
Encyclopedia
Flash photolysis is a pump-probe laboratory technique, in which a sample is firstly excited by a strong pulse (called pump pulse) of light from a laser
of nanosecond
, picosecond
, or femtosecond pulse width or by a short-pulse light source such as a flash lamp. This first strong pulse starts a chemical reaction
or leads to an increased population for energy levels other than the ground state within a sample of atoms or molecules. Typically the absorption of light by the sample is recorded within short time intervals (by a so-called test pulses) to monitor relaxation or reaction processes initiated by the pump pulse.
Flash photolysis was developed shortly after World War II
as a result of the military's attempts to build cameras fast enough to photograph missiles in flight. The technique was developed in 1949 by Manfred Eigen
, Ronald George Wreyford Norrish
and George Porter
, who won the 1967 Nobel Prize in Chemistry
for this invention. Over the next 40 years the technique became more powerful and sophisticated due to developments in optics and lasers. Also, the interest in this method grew considerably as the practical applications expanded from chemistry to areas such as biology, materials science, and environmental sciences. Today flash photolysis facilities are extensively used by researchers to study light-induced processes in organic molecules, polymer
s, nanoparticle
s, semiconductor
s, photosynthesis
in plants, signaling, and light-induced conformational changes in biological systems.
Makers of flash photolysis instruments:
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
of nanosecond
Nanosecond
A nanosecond is one billionth of a second . One nanosecond is to one second as one second is to 31.7 years.The word nanosecond is formed by the prefix nano and the unit second. Its symbol is ns....
, picosecond
Picosecond
A picosecond is 10−12 of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 001 seconds. A picosecond is to one second as one second is to 31,700 years....
, or femtosecond pulse width or by a short-pulse light source such as a flash lamp. This first strong pulse starts a chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
or leads to an increased population for energy levels other than the ground state within a sample of atoms or molecules. Typically the absorption of light by the sample is recorded within short time intervals (by a so-called test pulses) to monitor relaxation or reaction processes initiated by the pump pulse.
Flash photolysis was developed shortly after World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
as a result of the military's attempts to build cameras fast enough to photograph missiles in flight. The technique was developed in 1949 by Manfred Eigen
Manfred Eigen
Manfred Eigen is a German biophysical chemist who won the 1967 Nobel Prize in Chemistry for work on measuring fast chemical reactions.-Career:...
, Ronald George Wreyford Norrish
Ronald George Wreyford Norrish
Ronald George Wreyford Norrish was a British chemist. He was born in Cambridge and attended The Perse School. He was a former student of Eric Rideal...
and George Porter
George Porter
George Hornidge Porter, Baron Porter of Luddenham, OM, FRS was a British chemist.- Life :Porter was born in Stainforth, near Thorne, South Yorkshire. He was educated at Thorne Grammar School, then won a scholarship to the University of Leeds and gained his first degree in chemistry...
, who won the 1967 Nobel Prize in Chemistry
Nobel Prize in Chemistry
The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...
for this invention. Over the next 40 years the technique became more powerful and sophisticated due to developments in optics and lasers. Also, the interest in this method grew considerably as the practical applications expanded from chemistry to areas such as biology, materials science, and environmental sciences. Today flash photolysis facilities are extensively used by researchers to study light-induced processes in organic molecules, polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s, nanoparticle
Nanoparticle
In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size : in terms of diameter, coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are sized...
s, semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
s, photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
in plants, signaling, and light-induced conformational changes in biological systems.
External links
- Nobel Prize: Chemistry 1967
Makers of flash photolysis instruments: