mJcm

mJcm is an informal, non-SI unit that has appeared in some technical literature to denote milliJoules per centimeter, i.e., energy delivered per unit length along a line or strip. It is not a standardized unit, and its meaning can vary depending on context. The conventional SI unit for energy per length is joules per meter (J/m).

Notation and conversion: When mJ/cm is used, 1 mJ/cm equals 0.1 J/m. Conversely, 1 J/m equals 10 mJ/cm. If energy is given over a finite length L in centimeters, the total energy E in millijoules is E (mJ) = (energy density in mJ/cm) × L (cm).

Usage: mJ/cm may appear in descriptions of energy deposition along a line in optical, laser, or photothermal applications, where a laser pulse deposits energy along a trench or along a fiber. It may also be used in dose measurements along a line in some material testing or in microfabrication charts. However, because it is ambiguous and nonstandard, many authors prefer mJ/cm^2 (dose per area) or convert to J/m for clarity.

Example: A laser delivers 5 mJ over a 2 cm segment. The energy per length is 2.5 mJ/cm, equivalent to 0.25 J/m. If instead the report is for a surface dose over a 2 cm by 2 cm area, a mJ/cm^2 value would be used instead.

See also: Dosimetry units, Energy density, Joule per meter, Millijoule.