integrated intensity 

https://doi.org/10.1351/goldbook.08258
Area under a spectral band in an absorption spectrum where the absorption is linearly proportional to the amount of absorber in unit area.
Notes:
  1. The area under a band in a transmittance spectrum is not linearly proportional to the amount of absorber.
  2. The absorption quantity is usually a Beer-Lambert absorption coefficient, but recently ν~αm(ν~), the wavenumber times the imaginary part of local molar polarizability, has been used for neat liquids to correct for dielectric effects.
Source:
PAC, 2021, 93, 647. (Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)) on page 662 [Terms] [Paper]