2007 Fiscal Year Final Research Report Summary
Theoretical study on quantum control of photo-induced electron and nuclear dynamics of chiral molecules and generation of their functionality
| Project/Area Number |
17350004
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Physical chemistry
|
|---|
| Research Institution | Tohoku University |
|---|
Principal Investigator |
FUJIMURA Yuichi Tohoku University, Emeritus Professor (90004473)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
KONO Hirohiko Graduate School of Science, 大学院・理学研究科, Professor (70178226)
HOKI Kunihito Graduate School of Science, 大学院・理学研究科, Assistant Professor (00436081)
|
|---|
| Project Period (FY) |
2005 – 2007
|
| Keywords | molecular motor / quantum control / molecular chirality / femtosecond dynamics / π-electron current / electron wave packet / π-electron rotation / nuclear wave packet |
|---|
| Research Abstract |
Recently considerable attention has been directed to control of ultra-fast electron and nuclear dynamics in photo-excited molecules. Especially, electron and unclear dynamics of chiral molecules are fascinating targets for generation of functionality such as molecular motors, switching and electron currents since these are induced by asymmetric electronic and nuclear potentials. In this project, we paid our attention to two subjects: (a) theoretical design of femto-second unidirectional rotation of molecular motor by using a quantum control method; (b) theoretical proposal of generation of pi-electron currents in chiral molecules by applying linearly polarized UV lasers.
(a) A quantum optimal control simulation of a chiral molecular motor driven by femtosecond UV laser pulses was performed. A chiral molecule, (R)-2-methyl-cyclopenta-2, 4-dienecarboaldehyde, via the first singlet (nπ^*) excited state S_1 was treated as a molecular motor. Here, the aldehyde group acts as a roror part of t
… More
he motor. Electric fields of femtosecond laser pulses driving both the regular rotation with a plus angular momentum and the reverse rotation with a minus one have been designed by using a global control method. The mechanisms of the unidirectional rotations have been clarified by analyzing the time-frequency-resolved spectrum of the electric fields of the optimal laser pulses and by resolving the temporal behaviors of rotational wave packets both in S_0 and S_1. The mechanism of the regular rotation is similar to that obtained by a conventional pump-dump pulse method. A new control mechanism has been proposed for the reverse rotation that cannot be driven by a simple pump-dump pulse method.
(b) We have demonstrated that π electrons in a chiral aromatic molecule can be rotated along its ring by using a linearly polarized laser pulse. This indicates that molecular chirality can also be a source of directional ring currents because a nonhelical photon has no angular momentum. π-Electron dynamics reflects the asymmetry of the molecule itself. We have shown that the rotation direction of π electrons depends on the polarization direction of the applied pulse relative to the spatial configuration of each enantiomer on the basis of a three-level model analysis. We have performed optimal control simulations of π-electron rotation (ring current) in a six-membered control pulse at the maxima is a two-color laser field resonant with the quasi-degenerate states. The relative phase between the two frequency components is a crucial parameter for determination of the rotation direction of π-electrons at the end of control. Control scheme of π-electron rotation suggested by optimal control simulations is control in frequency domain by a two-color laser field while π-electron rotation can also be controlled in time domain by a central-peak laser pulse, e.g., a sin^2 or Gaussian pulse.
In this research project, we have developed a fundamental basis of control of ultrafast electrons and vibrational states of chiral molecules by using linearly polarized lasers. Less
|
Research Products
(27 results)
