High-resolution spectroscopy of buffer-gas-cooled phthalocyanine

Strong parity-violation effects induced by large-amplitude motions: A quantum-dynamics study of substituted chiral methanols

An enhanced mechanism is proposed for the large-amplitude-motion-induced parity-violating frequency by integrating the exact quantum dynamics method with the relativistic electronic structure theory. The torsional wavefunctions and parity-violating (PV) frequency shifts are obtained by using the exact quantum dynamics method. The potential energy curve and PV energy along the torsional coordinates are calculated using the extended atomic mean-field two-component Hamiltonian. The predicted PV frequency shift for the torsional transition of CFClBrOH is ∼100 times larger than that of the conventional C-F stretching mode of CHFClBr. The maximum PV frequency shift (3.2 Hz) is obtained in the CHBrIOH molecule.

Analysis on high-resolution spectrum of the S1-S0 transition of free-base phthalocyanine

A high-resolution absorption spectrum of the S1-S0 transition of free-base phthalocyanine was observed and analyzed with improved reliability. The spectrum, with a partially resolved rotational structure, was obtained by using the buffer-gas cooling technique and a single-mode tunable laser. Our new analysis reveals that the S1←S0000 band belongs to the a-type transition, where the electronic transition moment aligns parallel to the NH-HN direction, allowing the assignment of the S1 state to 1B3u. These results agree with a prior study using supersonic expansion and are well supported by theoretical calculations. Interestingly, the rotational constant B in the S1 state, which is often smaller than that in the ground state for typical molecules, was found to be slightly larger than that in the S01Ag state. This suggests a change in the character of π bonds with the electronic excitation.