Single-molecule laser nanospectroscopy with micro–electron volt energy resolution

Abstract

Ways to characterize and control excited states at the single-molecule and atomic levels are needed to exploit excitation-triggered energy-conversion processes. Here, we present a single-molecule spectroscopic method with micro–electron volt energy and submolecular-spatial resolution using laser driving of nanocavity plasmons to induce molecular luminescence in scanning tunneling microscopy. This tunable and monochromatic nanoprobe allows state-selective characterization of the energy levels and linewidths of individual electronic and vibrational quantum states of a single molecule. Moreover, we demonstrate that the energy levels of the states can be finely tuned by using the Stark effect and plasmon-exciton coupling in the tunneling junction. Our technique and findings open a route to the creation of designed energy-converting functions by using tuned energy levels of molecular systems.

Internal Stark effect of single-molecule fluorescence

“…These shifts may originate from several physical effects. Due to the presence of the STM tip generating external static and dynamic electrical fields, Stark and photonic Lamb effects may contribute to the observed energy shifts 18 , 45 – 48 . However, recent STML and photoluminescence works demonstrated that these effects may at best lead to few meV shifts of the emission maxima 18 , 48 , and cannot explain the large blue shifts reported in Fig.…”

Optical Images of Molecular Vibronic Couplings from Tip-Enhanced Fluorescence Excitation Spectroscopy

“…In the simulations we have neglected the finite temperature effect because the STM-PL experiments were efficiently performed only under cryogenic temperatures. 17 , 18 The vibrational integrals were computed with the DynaVib software. 62…”

“…Specifically, the TEFE spectra and images in Figure 2 were broadened with a full-width at half-maximum (fwhm) of 5.00 meV. For high-order vibrational transitions, a smaller fwhm of 0.50 meV, which has been obtained very recently in STM-based photoluminescence excitation spectroscopy, 18 was used to better locate the weak combinational transitions.…”

Development of nano- and microdevices for the next generation of biotechnology, wearables and miniaturized instrumentation

“… 131 Other examples based on other signals could be mentioned as well, such as single-molecule laser nanospectroscopy with micro-electron volt energy resolution. 132 Therefore, the importance of the future of optics in life sciences and its related technological impact was shown. 133 …”