For optically active substances the ionization yield for left and right circularly polarized light is different. We present mass resolved multi photon ionization CD (MPI-CD) spectra of (+)- and (-)-3-Methylcyclopentanone (3-MCP) and other carbonyles. The electronically forbidden, but magnetically allowed Ï€*←n-transition of 3-MCP shows a very strong relative CD in ion yield which makes this substance ideally suited for basic investigations. When ionizing 3-MCP with 1+1+1 MPI via the Ï€* state, the mol. fragments heavily. Only 50-400 ions per laser pulse are produced. This results in the need of averaging several hundred pulses in order to achieve good statistics. Under this conditions measurements down to values of about 0.5     «

For optically active substances the ionization yield for left and right circularly polarized light is different. We present mass resolved multi photon ionization CD (MPI-CD) spectra of (+)- and (-)-3-Methylcyclopentanone (3-MCP) and other carbonyles. The electronically forbidden, but magnetically allowed Ï€*←n-transition of 3-MCP shows a very strong relative CD in ion yield which makes this substance ideally suited for basic investigations. When ionizing 3-MCP with 1+1+1 MPI via the Ï€* state,...     »