Hi! The green house gases don't absorb heat at all wavelengths. The major contributor i.e. Carbon dioxide absorbs heat (infrared radiation) in narrow bands near 1.4,1.9, 2, 2.3, 4.3 & 15 micrometers wavelengths. You can search for 'absorption spectra of Atmosphere.' I have gone through a paper (http://jvarekamp.web.wesleyan.edu/CO2/FP-1.pdf) that details about measurement of Transmittance of near-infrared radiations through a chamber filled with various ratios of a mixture of Carbon dioxide & Nitrogen.