F

F

atomic symbol for fluorine

false acceptance

type II error

false negative

type II error

false positive

type I error

false rejection

type I error

F distribution

A type of probability distribution. If V and W are independent chi-squared random variables, with k and m degrees of freedom respectively, then (V / k) / (W / m) has the F distribution with k and m degrees of freedom.

Fe

atomic symbol for iron

filtrate

material (generally liquid) that has passed through a filter

fission

See nuclear fission

fission product

radionuclide produced directly or indirectly by nuclear fission

fluor

material that emits a short burst of light in response to incident radiation (see also phosphor and scintillator)

fluorescence

luminescence which occurs essentially only during the irradiation of a substance by electromagnetic radiation [IUPAC]

flux

substance that promotes fusion of one or more other substances by lowering their melting points

Fm

atomic symbol for fermium

fossil water

groundwater that has remained in an aquifer for millennia

Fr

atomic symbol for francium

fractional shoveling

technique for splitting a material lot (e.g., of soil) into two or more fractions, in which small scoops of material are removed and deposited in containers in a repeating sequence until all the material has been deposited

Fractional shoveling is intended to ensure that each fraction tends to be representative of the lot.

full-energy peak

in a gamma-ray spectrum, a peak pro­duced when incident gamma-rays of a given energy deposit all of their energy in the detector

full width at half maximum (FWHM)

width of a spectral peak at half its height above the baseline, often used as a measure of peak resolution

If the peak shape is Gaussian, the full width at half maximum is related to the standard deviation, σ, of the Gaussian distribution as follows:

FWHM = 2.355 × σ

full width at tenth maximum (FWTM)

width of a spectral peak at one-tenth its height above the baseline, often used as a measure of peak resolution or tailing

If the peak shape is Gaussian, the full width at tenth maximum is related to the standard deviation, σ, of the Gaussian distribution as follows:

FWTM = 4.292 × σ

Note: In general the full width at (1/k) maximum, for k ≥ 1, is given by

FW(1/k)M = σ ×

√

8 × ln k

fundamental error

relative error of sampling due to the constitutional heterogeneity of the lot of material being sampled, which depends on the masses of the lot and the sample, the com­po­sition of the material, and the sizes of the particles, but which does not depend on the spatial arrange­ment of the particles and thus is un­affected by mixing

fusion

1. melting (as in heat of fusion)
2. act or process of using heat to liquefy or plasticize material
3. technique for decomposing sample material for analysis using heat and often a flux to melt the material
4. nuclear fusion