Figure 1

Fluorescence excitation spectrum at $T=1.7\mathrm{K}$ for three single DBATT molecules embedded in a hexadecane layer deposited on a 50 nm thick niobium substrate. The spectrum is recorded at an excitation intensity well below saturation. Two sharp lines display a nearly surface-unaffected linewidth ($\sim 20\mathrm{MHz}$). The broad Lorentzian line has a linewidth of 1.1 GHz.Reuse & Permissions

Figure 2

LIS of a single molecule of DBATT in hexadecane near a 50 nm indium layer at 1.7 K. (a) Fluorescence excitation spectra recorded at increasing excitation intensities from bottom to top (steps of $20\mathrm{W}{\mathrm{cm}}^{-2}$). The top spectrum is recorded after the series at the same intensity as the bottom spectrum ($6\mathrm{W}{\mathrm{cm}}^{-2}$). (b) Line broadening with excitation intensity. A fit by a two-level system optical saturation law gives $\Delta {\nu }_{\mathrm{hom}}=18\mathrm{MHz}$ and $I_{\mathrm{sat}}=1.6\mathrm{W}{\mathrm{cm}}^{-2}$. (c) Dependence of the LIS on the excitation intensity. The LIS slope is $1.3\mathrm{MHz}/(\mathrm{W}{\mathrm{cm}}^{-2})$, i.e., $0.11\Delta {\nu }_{\mathrm{hom}}$ per saturation intensity. (d) LIS dependence on the laser linear polarization which is rotated in a plane parallel to the metallic layer, at a fixed excitation intensity of $120\mathrm{W}{\mathrm{cm}}^{-2}$. The dependence is well fitted with ${\cos }^2\theta$, $\theta$ being the angle between the laser field and the transition dipole projection onto the metal surface plane.Reuse & Permissions

Figure 3

Effect of transition dipole dephasing on the LIS for a single DBATT molecule in hexadecane near a 50 nm gold layer. The LIS slope is measured for different temperatures, varied between 1.8 and 4.2 K, and plotted as a function of the temperature dependent homogeneous width. The experimental points are fitted by a function inversely proportional to homogeneous width.Reuse & Permissions

Figure 4

Series of excitation spectra for several single molecules of DBATT in hexadecane near a 50 nm gold layer, at $T=1.7\mathrm{K}$. The corresponding excitation intensity is reported on the right scale. The molecule presenting a large LIS effect (slope of $11\mathrm{MHz}/(\mathrm{W}{\mathrm{cm}}^{-2})$) undergoes a turning point in the shift at high excitation intensity (higher than $\sim 100I_{\mathrm{sat}}$).Reuse & Permissions