title: Electric field gradient quadrupole Raman modes observed in plasmon-driven catalytic reactions revealed by HV-TERS.
abstract: Electric field gradient quadrupole Raman modes are observed in plasmon-driven chemical reactions investigated with high vacuum tip-enhanced Raman spectroscopy (HV-TERS). TER spectra reveal that 4-nitrobenzenethiol (4NBT) catalytically dimerizes to dimercaptoazobenzene (DMAB) under an HV-TERS setup. More importantly, we find that the electric field gradient leads to strong enhancement of the infrared (IR)-active modes of DMAB. The observation of both the Raman-active and IR-active modes of DMAB provides spectral evidence for ultrasensitive chemical analysis.
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P. O. Box 603-146, Beijing, 100190, People's Republic of China.
authors.forename: Zhenglong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Mengtao
authors.initials: M
authors.lastname: Sun
authors.forename: Panpan
authors.initials: P
authors.lastname: Ruan
authors.forename: Hairong
authors.initials: H
authors.lastname: Zheng
authors.forename: Hongxing
authors.initials: H
authors.lastname: Xu