Our latest article with the title ‘Studies of the First Electronically Excited State of 3-Fluoropyridine and its Ionic Structure by Means of REMPI, Two-Photon MATI, One-Photon VUV-MATI Spectroscopy and Franck-Condon Analysis ’ just got published in Phys. Chem. Chem. Phys.!
This is a follow-up article to our previous work on 3-chloropyridine utilizing Niklas’ new one-photon VUV-MATI setup.
Abstract: 3-Fluoropyridine (3-FP) has been investigated by means of two-photon resonance-enhanced multi photon ionization (REMPI), mass-analyzed threshold ionization (MATI) and one-photon vacuum-ultraviolet (VUV) MATI spectroscopy. The aim was the determination of the effect of m-fluorine substitution on the vibronic structure of the first electronically excited and ionic ground state. The S1 excitation energy has been determined to be 35064 ± 2 cm-1 (4.3474 ± 0.0002 eV). Strong evidence of a distinct vibronic coupling via ν16b and ν[Wag.out.,16a] to one or both of the lowest 1ππ* states have been found, which results in a warped S1 minimum structure with C1 symmetry. The adiabatic ionization energy of the ionic ground state (14a’, nN-LP¬ orbital) has been determined to be 76579 ± 6 cm-1 (9.4946 ± 0.0007 eV), which is the first value reported for this state. The origin of the D1 state (4a’’, π-orbital) is located close by at 77129 cm-1 (9.5628 eV). As a result of the D0-D1 vicinity, the ionic ground state is coupled to the D1 state via ν[Wag.out.,16a] and ν10a, which induces a twisted D0 geometry with C1 symmetry. Furthermore, for the first time two-photon and one-photon MATI spectra are presented together, which yield a much better understanding of the ionic vibronic structure in comparison to either of these experiments alone.
The article is now available online: https://doi.org/10.1039/D1CP04636E