Circular dichroism resonance enhanced multiphoton ionization time-of-flight mass spectrometry (CD REMPI TOF MS) is an extraordinary sensitive and selective method to record high resolution UV and CD spectra of cold molecules in the gas phase. However, many (bio)molecules of interest are not volatile and thermally labile. Transferring them into the gas phase therefore presents a challenge. Here laser desorption was combined with REMPI at the example of 1,1’-Bi-2-naphtol (BINOL). For that, the experimental setup from a previous work(1) was modified. Cylindrical lenses were implemented into the beam paths of desorption and ionization. The adiabatic cooling was improved by replacing the previous general valve with a larger one. As a result, the sensitivity and signal stability got strongly enhanced. The temperature of the molecular beam however, could not be decreased sufficiently. Experimental results indicate that this is due to the fact that laser desorption of BINOL at 607 nm is mainly thermal leading to very hot desorbed molecules. This affects the achievable spectral resolution, and a solution to overcome this issue will be presented.

(1) J. Lepelmeier, J. L. Alonso-Gómez, F. Mortaheb, U. Boesl, U. Heiz and A. Kartouzian, Chiroptical inversion for isolated vibronic transitions of supersonic beam-cooled molecules, Phys. Chem. Chem. Phys., 2017, 19, 21297–21303.