Radiant exposure is a measure of the total radiant energy incident on a surface per unit area; equal to the integral over time of the radiant flux density. Also known as exposure.
Applicable units are those of quantitykind:EnergyPerArea
http://omlc.ogi.edu/education/ece532/class1/irradiance.html
https://cdd.iec.ch/cdd/iec61987/iec61987.nsf/ListsOfUnitsAllVersions/0112-2---62720%23UAD150
Radiant exposure is a measure of the total radiant energy incident on a surface per unit area; equal to the integral over time of the radiant flux density. Also known as exposure.
$H = \int_{0}^{\Delta t}{E}{dt}$, where $E$ is the irradiance acting during the time interval with duration $\Delta t$.