Molecular Dipole Chains III:  Energy Transfer

Abstract

Energy transfer in initially excited dipole chains was studied using simple one-dimensional models. Two types of chains were studied: the altitudinal dipole chain, in which all the dipoles rotate around the same axis, and the azimuthal dipole chain, in which the chain axis lies in the rotation planes of the dipoles. The analytic treatment of a pair of dipoles shows that energy transfer from dipole to dipole can only be complete for low excitations. At higher excitations, the excited dipole rotates too quickly for the second one to follow. Molecular dynamics simulations of 25-dipole chains show that energy transfer is possible in these chains. In some limiting cases, the energy transfer shows a soliton-like behavior. The altitudinal chain shows such behavior for low excitations, but for high excitations the rest of the chain cannot follow the excited dipole. In the azimuthal chain, the soliton-like behavior is more difficult to find: Both for low and high excitations the system shows no noticeable energy transfer. Only for certain excitations with intermediate energy can a soliton-like transfer be observed.

Artificial Molecular Rotors

“…151 Ratner, de Leeuw, and co-workers have modeled one-dimensional arrays of dipolar rotators as classical point dipoles with no torsional potential or friction. [81][82][83] As might be expected from eq 6, the ground state of this system occurs when all the dipole moments point along a line. 82 A more rigorous result considering long-range dipole-dipole effects gives the minimum energy, V min , as for a long chain of N dipoles separated by a distance r. 82 In contrast, for a chain of rotators where the axis of rotation is along the line connecting the rotators, the dipoles cannot point along a line and the ground state occurs when each dipole is antiparallel to its neighbors.…”

“…81 In Figure 4, which shows the maximum (50) energy of the 10th dipole in the chain as a function of excitation energy of the first dipole, the difference of the coaxial and the coplanar chains is obvious. Low-energy excitations below three reduced energy units (E × 4π 0 r 3 /µ 2 ), which are essentially blocked in the coplanar chain, propagate through the coaxial chain as a soliton-like wave.…”

Artificial Surface‐Mounted Molecular Rotors: Molecular Dynamics Simulations

“…[20,22,23] 1D arrays have also been studied. [24][25][26] The rotor arrays examined experimentally so far were irregular, [6] usually with the rotors far enough apart that their mutual interaction was negligible. This is like studying a single rotor, [27] and the present feature article is concerned above all with the design and performance of individual surface-mounted molecular rotors.…”

Analysis of the classical phase space and energy transfer for two rotating dipoles with and without external electric field

“…[22][23][24][25][26][27][28], the question concerning the energy sharing mechanism in a chain of nonlinear oscillators, and, therefore, in a many-body system, can be considered still an open question. Furthermore, in references [17][18][19] the energy flow in a linear chain of interacting rotating dipoles and in a two-dipole system are explored. For the two-dipole system, the authors conclude the existence of a critical excitation energy up to which there is no energy transfer.…”