An introduction to the principle and possibilities of the new method of circular dichroism laser mass spectrometry is given and its state of development is reviewed. This method allows enantiosensitive, mass-selective probing of chiral molecules. It is based on the combination of resonance-enhanced multiphoton ionization with circularly polarized light and specially modified time-of-flight mass spectrometry. As an example, application to carbonyls is presented.

An experiment on chiral molecules that combines circular dichroism (CD) spectroscopy, mass-selective detection by laser mass spectrometry (MS), and cooling of molecules by using a supersonic beam is presented. The combination of the former two techniques (CD-laser-MS) is a new method to investigate chiral molecules and is now used by several research groups. Cooling in a supersonic beam supplies a substantial increase in spectroscopic resolution, a feature that has not yet been used in CD spectroscopy. In the experiments reported herein, a large variation in the electronic CD of carbonyl 3-methylcyclopentanone was observed depending on the excited vibrational modes in the n → π* transition. This finding should be of interest for the detection of chiral molecules and for the theoretical understanding of the CD of vibronic bands. It is expected that this effect will show up in other chiral carbonyls because the n → π* transition is typical for the carbonyl group.

UV spectroscopy and electronic circular dichroism (ECD) experiments on supersonic-beam-cooled deuterated (R)-(+)-3-methylcyclopentanone ([D ]-(R)-(+)-3-MCP) have been performed by using a laser mass spectrometer. The spectral resolution not only allowed excitation and CD measurements for single vibronic transitions but also for the rotational P, Q, and R branches of these transitions. The investigated n→π*18042501 transition showed the largest anisotropy factor ever observed for chiral molecules in the gas phase, which, due to residual saturation of the excited transition, represents only a lower limit for the real anisotropy factor. Furthermore, one-color (1+1+1) and two-color (1+1') resonance-enhanced multiphoton ionization (REMPI) measurements were performed and the effusive-beam (room temperature) and supersonic-beam results for [D ]-(R)-(+)-3-MCP were compared. These results allowed a differentiation between single-step ECD (comparable to conventional ECD) and cumulative ECD (only possible in multiphoton excitation) under supersonic-beam conditions.

Cooling of chiral molecules in a laser mass spectrometer experiment allows selective excitation of vibrations in the electronic excited state to reveal a strong influence of special vibrations on the electronic circular dichroism, as reported on p. 2762 by U. Boesl et al.

The Inside Cover picture shows a mass–wavelength spectrum of room‐temperature d4‐CP and supersonic beam‐cooled d4‐3‐MCP measured simultaneously with CD‐REMPI. One of the vibronic transitions of d4‐3‐MCP possesses the highest anisotropy factor ever detected. More information can be found in the Full Paper by A. Kartouzian and co‐workers on page 4052 in Issue 24, 2016 (DOI: 10.1002/cphc.201600811).