  For over five decades, studies in the field of chemical physics and physical
chemistry have primarily aimed to understand the quantum properties of
molecules. However, high-resolution rovibronic spectroscopy has been limited to
relatively small and simple systems because translationally and rotationally
cold samples have not been prepared in sufficiently large quantities for large
and complex systems. In this study, we present high-resolution rovibronic
spectroscopy results for large gas-phase molecules, namely, free-base
phthalocyanine (FBPc). The findings suggest that buffer-gas cooling may be
effective for large molecules introduced via laser ablation. High-resolution
electronic spectroscopy, combined with other experimental and theoretical
studies, will be useful in understanding the quantum properties of molecules.
These findings also serve as a guide for quantum chemical calculations of large
molecules.
