recombination time

recombination time

The period in the Universe's history, according to the Big Bang theory, after which the temperature was low enough for atoms to form from free nuclei and electrons. This required a temperature of less than about 3000 K, which occurred when the Universe had expanded for about 300 000 years. At the time of recombination the radiation in the Universe began to propagate freely and ceased to interact with free electrons. This freely propagating radiation now resides in the microwave background. The name ‘recombination’ is a misnomer because neutral atoms are formed for the first time at the recombination era, never having existed previously.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
References in periodicals archive ?
The addition of transitional metals to Ti[O.sub.2] seeks to increase the recombination time of electron/hole pair during electronic excitation [10, 11].
The use of Pd as a dopant in Ti[O.sub.2] was evaluated on C[O.sub.2] hydrogenation under UV irradiation generating the amount of 355.62 [micro]mol C[H.sub.4]/g-cat by the increase of recombination time of generated electrons and adsorption and activation of C[O.sub.2] molecules on surface of catalyst [17].
(8) Photo-generated electron-hole pairs have a recombination time of the order of [10.sup.-9] s; however, the chemical interaction with adsorbed pollutant species has a timescale of [10.sup.-8] to [10.sup.-3] s.
This technique in principle is a large perturbation technique used to extract information on the recombination time and mechanism in the DSSC.
Because the transport mainly occurs through bulk trap states, the recombination time is prolonged by one order of magnitude considering that the electrons are caught and released much faster from surface than from bulk trap states.
The agility of the plasma mirror, in comparison, is mainly determined by the speed with which the magnetic field can be changed and by the recombination time, which is typically [less than or equal to] 10 [micro]sec.
Since these recombination times are typically less than 10 [micro]sec, the switching time between successive mirror orientations may also be less than 10 [micro]sec if the volume magnetic field can be changed on these time scales.
If the required electrical pulse length is longer than the recombination time, as can be the case with
GaAs (recombination time 1 ns), then the optical energy required to keep the switch closed is increased since carriers have to be generated within the switch continually.
The electron transit time ([[tau].sub.r]) and electron recombination time ([[tau].sub.r]) can be determined using the equations [[tau].sub.t] = 1/2[pi][f.sub.min] and [[tau].sub.r] = 1/2[pi][f.sub.min'].
If the required electrical pulse length is longer than the recombination time, as can be the case with GaAs (recombination time 1 ns), then the optical energy required to keep the switch closed is increased since carriers have to be generated within the switch continually.