Rotation-vibration motion of extremely flexible molecules – The molecular superrotor

Quasistructural molecules

“…Even though the particle can move freely along the edges of the quantum graph, the important features of the PES of CH are implicitly taken into account in the quantum‐graph model as the connectivity is determined by the shape of the PES. Another related and promising approach to interpret the rovibrational energy‐level pattern of the quasistructural CH molecule is the recently developed five‐dimensional rigid‐rotor model …”

“…Another related and promising approach to interpret the rovibrational energy-level pattern of the quasistructural CH + 5 molecule is the recently developed five-dimensional rigid-rotor model. [212][213][214] 6.…”

Tagging effects on the mid-infrared spectrum of microsolvated protonated methane

“… 11 Yet, largely unexplained remain the available high-resolution vibrational spectra 5 , 12 , 37 , 40 , 41 of bare CH 5 + , which continue to challenge state-of-the-art theoretical rovibrational spectroscopy. 42 – 46 …”

Rovibrational quantum dynamical computations for deuterated isotopologues of the methane–water dimer

“…The rovibrational computations reproduce fine details of and provide an assignment to many experimental features. Most interestingly, the experimentally observed reversed rovibrational sequences (whereby within the usual molecular picture one would assign a "negative" rotational energy to a vibrational state, a characteristic feature of certain floppy molecular systems [5][6][7][8][9][10][11]) were also obtained in the computations.…”

“…Furthermore, Refs. [8,10,11] In the present work, we take a simple strategy to better understand the origin of the splitting pattern and these formally negative-energy rotational excitations: besides the rigid-rotor model, which underlies the assignment and the observation of these reversed sequences, we use the coupled-rotor system as another meaningful model for weakly interacting dimers. The computed coupled-rotor decomposition (CRD, introduced in Section III) tables provide detailed information about the monomers' rotational states and their relative rotation within the rotating dimer.…”