Planar boron clusters B11−, B13+, B15+, and B19− have been introduced recently as molecular Wankel motors or tank treads. Here we present a universal mechanism for these dynamically fluxional clusters; that is, they are molecular rotors with inner wheels that rotate almost freely in pseudo-rotating outer bearings, analogous to rotating molecules trapped in pseudo-rotating cages. This mechanism has significant quantum mechanical consequences: the global-minimum structures of the clusters have C2v symmetry, whereas the wheels rotating in pseudo-rotating bearings generate rosette-type shapes with D9h, D10h, D11h, and D13h symmetries. The related rotational/pseudo-rotational energies appear with characteristic band structures, effecting the dynamics.

Tunneling isomerization of molecules with symmetric double well potentials are associated with periodic nuclear fluxes, from the reactant R to the product P and back to R. Halfway between R and P the fluxes achieve their maximum values at the potential barrier. For molecules in the lowest tunneling doublet (v = 0) the rises and falls to and from the maximum values are approximately bell-shaped. Upon excitation to higher tunneling doublets v = 1, 2, etc., however, this shape is replaced by symmetric “staircase patterns” of the fluxes, with v + 1 stepping up and down in the domains of R and P, respectively. The quantum derivation of the phenomenon is universal. It is demonstrated here for a simple model of nuclear fluxes during tunneling isomerization of ammonia along the umbrella inversion mode, with application to separation of isotopomers.

We present quantum dynamics simulations of the concerted nuclear and electronic densities and flux densities of the vibrating H2+ ion with quantum numbers 2Σg+, JM = 00 corresponding to the electronic and rotational ground state, in the laboratory frame. The underlying theory is derived using the nonrelativistic and Born–Oppenheimer approximations. It is well-known that the nuclear density of the nonrotating ion (JM = 00) is isotropic. We show that the electronic density is isotropic as well, confirming intuition. As a consequence, the nuclear and electronic flux densities have radial symmetry. They are related to the corresponding densities by radial continuity equations with proper boundary conditions. The time evolutions of all four observables, i.e., the nuclear and electronic densities and flux densities, are illustrated by means of characteristic snapshots. As an example, we consider the scenario with initial condition corresponding to preparation of H2+ by near-resonant weak field one-photon-photoionization of the H2 molecule in its ground state, 1Σg+, vJM = 000. Accordingly, the vibrating, nonrotating H2+ ion appears as pulsating quantum bubble in the laboratory frame, quite different from traditional considerations of vibrating H2+ in the molecular frame, or of the familiar alternative scenario of aligned vibrating H2+ in the laboratory frame.

Starting from a reaction path Hamiltonian, a suitably reduced harmonic bath averaged Hamiltonian is derived by averaging over all the normal mode coordinates. Generalization of the harmonic bath averaged Hamiltonian to any dimensions are performed and the feasibility to use a linear reaction path/surface are investigated and discussed. By use of a harmonic bath averaged Hamiltonian, the tunneling splitting and proton transfer dynamics of malonaldehyde is briefly discussed and shows that the harmonic bath averaged Hamiltonian is an efficient tool to capture quantum effects in larger systems.

Relativistic ab initio potential curves of RbCs lowest 1,3Σ+ states are calculated by diagonalizing the Douglas–Kroll–Hess Hamiltonian as implemented in Gaussian09 suite of programs. The ab initio calculations are performed at the CCSD(T) level with UGBS1P+ basis set, a huge all-electron basis set. The rovibrational eigenenergies and eigenfunctions on the lowest 1,3Σ+ ab initio potential curves are calculated by direct diagonalization of molecular Hamiltonian in a Fourier grid discrete variable representation. The results agree well with available experimental and theoretical work and the accuracy of theoretical descriptions of RbCs are increased, which is expected to be a good reference for further investigations.

•The control of adiabatic attosecond charge migration in benzene using rationally designed pulses is demonstrated.•The analysis of transient angular electronic fluxes is performed using wave function based methods.•The electronic phase aquired during the laser preparation step has a marked influence on the charge migration mechanism.We design four linearly x- and y  -polarized as well as circularly right (+) and left (−) polarized, resonant π/2π/2-laser pulses that prepare the model benzene molecule in four different degenerate superposition states. These consist of equal (0.5) populations of the electronic ground state S0(1A1g)S0(1A1g) plus one of four degenerate excited states, all of them accessible by dipole-allowed transitions. Specifically, for the molecule aligned in the xy  -plane, these excited states include different complex-valued linear combinations of the 1E1u,x1E1u,x and 1E1u,y1E1u,y degenerate states. As a consequence, the laser pulses induce four different types of periodic adiabatic attosecond (as) charge migrations (AACM) in benzene, all with the same period, 504 as, but with four different types of angular fluxes. One of the characteristic differences of these fluxes are the two angles for zero fluxes, which appear as the instantaneous angular positions of the “source” and “sink” of two equivalent, or nearly equivalent branches of the fluxes which flow in pincer-type patterns from one molecular site (the “source”) to the opposite one (the “sink”). These angles of zero fluxes are either fixed at the positions of two opposite carbon nuclei in the yz-symmetry plane, or at the centers of two opposite carbon-carbon bonds in the xz-symmetry plane, or the angles of zero fluxes rotate in angular forward (+) or backward (−) directions, respectively. As a resume, our quantum model simulations demonstrate quantum control of the electronic fluxes during AACM in degenerate superposition states, in the attosecond time domain, with the laser polarization as the key knob for control.

Tunneling isomerization of molecules with symmetric double well potentials are associated with periodic nuclear fluxes, from the reactant R to the product P and back to R. Halfway between R and P the fluxes achieve their maximum values at the potential barrier. For molecules in the lowest tunneling doublet (v = 0) the rises and falls to and from the maximum values are approximately bell-shaped. Upon excitation to higher tunneling doublets v = 1, 2, etc., however, this shape is replaced by symmetric “staircase patterns” of the fluxes, with v + 1 stepping up and down in the domains of R and P, respectively. The quantum derivation of the phenomenon is universal. It is demonstrated here for a simple model of nuclear fluxes during tunneling isomerization of ammonia along the umbrella inversion mode, with application to separation of isotopomers.