milliamu

Milliamu is a proposed or informal unit referring to one thousandth of the atomic mass unit (amu or u). It is not an officially standardized unit and is not widely used in scientific literature. When encountered, milliamu is typically written as mU or occasionally as mamu, but there is no universally accepted symbol or definition beyond the simple scaling from the atomic mass unit.

Relation to the atomic mass unit and conversions

One milliamu equals 1e-3 u. In SI units, this is 1.66053906660e-30 kilograms or 1.66053906660e-27 grams. Because 1 u is defined as 1 Da (dalton), 1 milliamu is also equal to 0.001 Da. In practical terms, mU is a very small fraction of a typical molecular mass; for example, the electron mass is about 0.000548579909 u, which is approximately 0.548579909 mU.

Usage and context

Milliamu is not part of the standard measurement system used in chemistry or physics. Most measurements and discussions of atomic and molecular masses use the unified atomic mass unit (u/Da) or kilograms/grams, depending on scale and precision. When a mass difference or quantity is needed at the level of a thousandth of an amu, authors may choose to express it in milliamu, but in many cases they simply use decimal fractions of u (for example, 0.001 u) or convert to Da or kilograms for clarity. The lack of official adoption means practitioners should define the unit explicitly if milliamu is used in a document.

See also

Atomic mass unit, Dalton, mass spectrometry, isotopes.