Optomechanical control of polar-molecule adsorption configurations by UV irradiation

Kowsalya Arumugam^1*, Abhishake Goyal¹, Hong-Ming Chen¹, Jing-Huan Dai¹, Mau-Fu Gao¹, Yasuo Nakayama², Tun-Wen Pi³, Sebastian Metz⁴, Theodoros A. Papadopoulos⁵, S.-J. Tang¹

¹Department of Physics and Astronomy, National Tsing Hua University, Hsinchu, Taiwan
²Department of Pure and Applied Chemistry, Tokyo University of Science, Chiba, Japan
³Physics, National Synchrotron Radiation Research Center, Hsinchu, Taiwan
⁴Scientific Computing Department, STFC Daresbury Laboratory, Warrington, UK
⁵Department of Natural Sciences, University of Chester, Chester, UK
⁶Institute of Physics, Academia Sinica, Taipei, Taiwan
⁷National Center for Theoretical Sciences, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Kowsalya Arumugam, email:kowsalya3691@gmail.com

Using photoemission spectroscopy (PES), we have systematically investigated the behavior of polar organic molecule, chloroaluminum phthalocyanine (ClAlPc), adsorbed in the Cl-down configuration on the Ag(111) substrate at the low temperature 77 K under UV irradiation with different photon fluxes. Judging from the evolution of photoemission spectral line shapes of molecular energy states (MES), we discovered that the Al-Cl dipoles anchor at Ag(111) hollow sites robustly so that the impinging photons don’t flip the ClAlPc molecules, which instead crouched down under radiation pressure with phthalocyanine (Pc) lobes bended down to interact with Ag atoms and induce charge transfer from them. Moreover, as photon flux is increased, the radiation pressure on the Pc plane starts reinforcing the tunneling of Al-Cl dipole through the plane to turn the adsorption configuration of ClAlPc from Cl-down to Cl-up, elucidating an optomechanical way of manipulating the dipole directions of polar molecules.

Keywords: Photon irradiation, Organic/Metal interface, Photoemission Spectroscopy, Chloroaluminium Pc, Low temperature