UV-VIS spectra of n-decanes
To the best of my knowledge, ordinary alkanes do not typically absorb anywhere in the UV/Vis region. The organic molecules that do typically contain electrons in $\pi$- or non-bonding orbitals, which have energy level transitions corresponding to UV/Vis wavelengths. That said, I did find one paper1 describing absorptions around the far UV ambit, where $\lambda &lt; 200\mathrm{nm}$.


DOI: 10.1021/jp903435c