Stable Single‐Molecule Lines of Terrylene in Polycrystalline para ‐Dichlorobenzene at 1.5 K

The spectroscopic properties of single terrylene (Tr) molecules are studied in a polycrystalline matrix of para ‐dichlorobenzene ( p ‐DCB) at 1.5 K. Samples grown in a glass capillary show a very strong site at 597 nm, which is redshifted by more than 700 cm −1 from the observed transition energy for Tr in p ‐DCB prepared as a film on a coverslip (572 nm). Each of these two sites is characterized by measuring their single‐molecule spectroscopic parameters at 1.5 K. Lifetime‐limited linewidths of 45±5 MHz are found for both sites. Fluorescence detection rates reach 8×10 4 count s −1 at saturation. The spectral trails of the majority of single molecules show no spectral jumps, indicating an absence of interacting two‐level systems; however, the small distribution of linewidths may indicate weak interactions with low‐frequency modes. Frequency jumps are observed for 10 % of the molecules. The complete emission spectra from two different single molecules at the center of each of the two sites is presented. Debye–Waller factors of α DW = 0.33±0.05 for the normal site (572 nm) and α DW = 0.30±0.05 for the red site (597 nm) are reported. This new host–guest system provides a quick and easy way to obtain lifetime‐limited single‐molecule lines.