Hi:) I don’t really understand why denser air is able to absorb more heat from longwave radiation compared to less dense air. anyone able to help ? Thanks:))!

The stratosphere rises above the tropopause.A layer of ozone molecules absorbs solar radiation, which heats the stratosphere. Unlike in the troposphere, the air in the stratosphere is stable because warmer, less dense air sits over cooler, denser air. As a result, there is little mixing of air within the layer.

(i used the layers as an example hope it helps)