CO2 phonon mode renormalization using phonon-assisted energy up-conversion

Nabila Tanjeem,Tadashi Kawazoe,Takashi Yatsui

doi:10.1038/srep03341

Abstract

Molecular dissociation under incident light whose energy is lower than the bond dissociation energy has been achieved through multi step excitation using a coupled state of a photon, electron, and multimode-coherent phonon as known as the dressed photon phonon (DPP). Here, we have investigated the effects of the DPP on CO2, a very stable molecule with high absorption and dissociation energies, by introducing ZnO nanorods to generate the DPP. Then, the changes in CO2 absorption bands were evaluated using light with a wavelength longer than the absorption wavelength, which confirmed the DPP-assisted energy up-conversion. To evaluate the specific CO2 modes related to this process, we measured the CO2 vibration-rotation spectra in the near-infrared region. Detailed analysis of the 3ν3 vibrational band when a DPP source is present showed that DPP causes a significant increase in the intensity of certain absorption bands, especially those that require higher energies to activate.

Highlights

Correspondence and requests for materials should be addressed to CO2 phonon mode renormalization using phonon-assisted energy up-conversion
Molecular dissociation under incident light whose energy is lower than the bond dissociation energy has been achieved through multi step excitation using a coupled state of a photon, electron, and multimode-coherent phonon as known as the dressed photon phonon (DPP)
The bond dissociation energy Ediss of one CO2 molecule has been reported to be more than 7 eV, equivalent to the energy of incident light wavelength of 174 nm

Summary

Introduction

Correspondence and requests for materials should be addressed to CO2 phonon mode renormalization using phonon-assisted energy up-conversion. We performed phononassisted energy up-conversion to dissociate CO2 molecules by introducing ZnO nanorods This process has been implemented previously for dissociating gas phase diethylzinc molecules using an optical near field generated around the nanostructure to stimulate multistep excitation via molecular vibrational modes under incident light with an energy less than the bond dissociation energy[5]. The physics of these nanoscale optical effects has been developed under the assumption of a conventional multipolar quantum electrodynamic Hamiltonian in a Coulomb gauge and of single-particle states in a finite nanosystem[6]. The result supports the assumption that DPP excitation permits CO2 molecules to absorb light with wavelengths longer than the absorption wavelength (l 5 213 . labs 5 200 nm)

Methods

Results

Conclusion