One and two-photon absorption circular dichroism of optically active chiral systems

Chiral molecules are typically optically active with inherently non-superimposable mirror images. Henceforth, these molecules can exhibit differences in absorption between left-and-right circularly polarized light. This difference in light absorption is terminologically called circular dichroism. In this paper, a comparative theoretical and spectroscopic study on the one-photon absorption circular dichroism (OPCD) and two-photon absorption circular dichroism (TPCD) of an optically active chiral ketone over the far and near-ultraviolet region is presented. As molecular transitions associated with OPCD and TPCD obey different selection rules with feasibly different spectral features, the two processes are thus complementary. The strengths and weaknesses of employing one and two-photon circular dichroism of R-(+)-3-Methylcyclopentanone to investigate optical activity are discussed. Moreover, the basic theory of OPCD and TPCD is also shown and compared against corresponding spectroscopic results.