P-process

The term p- process (p for proton) is used in the scientific literature for the study of astrophysical origin of the elements ( nucleosynthesis ) in two ways. Originally, the term of certain proton- rich isotopes of the heavy elements of selenium was a proton attachment process meant to produce mercury. These nuclides are called p-nuclei. Although it has been shown that the originally proposed p- process the p-nuclei can not produce, the term was later sometimes quite commonly used as a generic term for any Nukleosyntheseprozess which produces p-nuclei.

The mixing of the two meanings often leads to confusion. It is therefore proposed in the recent scientific literature, the term p- process only for the actual astrophysical Nukleosyntheseprozess to use (as it is also common in other processes ), so for of a proton under certain conditions.

The end of the process P

To produce proton- rich cores, the protons can be captured ( the so-called seed core ) on a nucleus of another element with lower atomic number. The original idea for the production of p-nuclei was therefore that such proton deposits on existing heavy elements in stars (which were previously produced in the s - and / or r-process ) take place.

However, such a proton capture can not generate p-nuclei, because with increasing number of protons in the nucleus of Coulombwall is higher, the need to overcome any new to be added proton. The higher the Coulombwall is, the more energy needs a proton to make it penetrate into the nucleus and can be trapped there. The mean energy of the protons is determined by the temperature of the stellar plasma. If the temperature is too high, protons from the nuclei struck by photodisintegration faster than they can be attached. As a way out, the presence of a large number of protons would be an opportunity, so that the effective number of captures per second is great, even if the temperature is not greatly increased. These conditions are (eg, core-collapse supernovae ) not found in the relevant astrophysical environments.

Historical

The p- process was originally proposed as a synthesis process of p-nuclei and it was thought he would run into the hydrogen envelope of exploding as core-collapse supernovae, massive stars. However, it was later shown that there the necessary conditions are not met. However, an alternative to a pure proton capture a pure photodisintegration process were considered in the former work, for example ( now called γ - process ) or a combination of p- process and photodisintegration.