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In this situation it is generally uncommon to talk about half-life in the first place, but sometimes people will describe the decay in terms of its "first half-life", "second half-life", etc., where the first half-life is defined as the time required for decay from the initial value to 50%, the second half-life is from 50% to 25%, and so on. [7]
Terms "partial half-life" and "partial mean life" denote quantities derived from a decay constant as if the given decay mode were the only decay mode for the quantity. The term "partial half-life" is misleading, because it cannot be measured as a time interval for which a certain quantity is halved.
One may integrate over the phase space to obtain the total decay rate for the specified final state. If a particle has multiple decay branches or modes with different final states, its full decay rate is obtained by summing the decay rates for all branches. The branching ratio for each mode is given by its decay rate divided by the full decay rate.
Carbon-14 has a half-life of 5700(30) years [27] and a decay rate of 14 disintegrations per minute (dpm) per gram of natural carbon. If an artifact is found to have radioactivity of 4 dpm per gram of its present C, we can find the approximate age of the object using the above equation:
Clearance of a substance is sometimes expressed as the inverse of the time constant that describes its removal rate from the body divided by its volume of distribution (or total body water). In steady-state, it is defined as the mass generation rate of a substance (which equals the mass removal rate) divided by its concentration in the blood.
One of the two naturally occurring isotopes of rubidium, 87 Rb, decays to 87 Sr with a half-life of 49.23 billion years. The radiogenic daughter, 87 Sr, produced in this decay process is the only one of the four naturally occurring strontium isotopes that was not produced exclusively by stellar nucleosynthesis predating the formation of the ...
The molar weight is 59.93. The half life T of 5.27 year corresponds to the activity A = N [ ln(2) / T ], where N is the number of atoms per mol, and T is the half-life. Taking care of the units the radiation power for 60 Co is 17.9 W/g Radiation power in W/g for several isotopes:
With the decay constant it is possible to calculate the effective half-life using the formula: t 1 / 2 = ln ( 2 ) λ e {\displaystyle t_{1/2}={\frac {\ln(2)}{\lambda _{e}}}} The biological decay constant is often approximated as it is more difficult to accurately determine than the physical decay constant.