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Coherence and Ultrashort Pulse Laser Emission Part 5

Tham khảo tài liệu 'coherence and ultrashort pulse laser emission part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 152 Coherence and Ultrashort Pulse Laser Emission cyclopentadiene with a chlorine atom as a main body. The aldehyde group can be driven by laser pulses but the trifluoromethyl group cannot be because it is optically inactive. In that sense the molecule can be regarded as one of the smallest molecular machines the motion of the aldehyde group as a motor and that of the trifluoromethyl group as a gear or a propeller. We note that there is no belt or chain which directly connects the motor and blades of the gear in contrast to a macroscopic fan. It would be interesting to see if the machine can work by irradiation of laser pulses and to determine how power is transmitted from the motor to the running propeller and what the transmission mechanism is if it works. Fig. 13. R -2-chloro-5-trifluoromethyl-cyclopenta-2 4-dienecarbaldehyde attached at a surface as a molecular machine. The C3 atom is a chiral center. The z-axis is defined to be along the C3-C2 bond. R4 denotes an alkyl group. A linearly polarized laser pulse propagating along the y-axis Ey t is applied. A torsional coordinate of the aldehyde group is denoted by Ộ and that of the trifluoromethyl group is labeled by X- Reproduced with permission from Phys. Chem. Chem. Phys. 11 1662 2009 . For the sake of simplicity we treat the quantum dynamics simulation of the molecular machine in a two-dimensional model in which one of the coordinates Ộ is regarded as that of the motor and another X is regarded as a running propeller. The coordinate Ộ is defined as a dihedral angle of the O1-C2-C3-R4 group and X is specified by a dihedral angle of the F7-C6-C5-C3 group as shown in Fig. 13. The z-axis is defined to be along the C3-C2 bond. The x-axis is defined to be on the C2-C3-R4 plane. The cyclopentadiene group which is the main body of the machine was assumed to be fixed on a surface to reduce the role of entire molecular rotations. In the actual simulation an alkyl group -R4 is replaced by -H for simplicity. 4.2 Results