Masoud Mirzaei M.Sc.

High-resolution vibronic spectroscopy of a single molecule embedded in a crystal

Johannes Zirkelbach, Masoud Mirzaei, Irena Deperasińska, Boleslaw Kozankiewicz, Burak Gürlek, Alexey Shkarin, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar

Vibrational levels of the electronic ground states in dye molecules have not been previously explored at high resolution<br>in solid matrices. We present new spectroscopic measurements on single polycyclic aromatic molecules of dibenzoter-<br>rylene embedded in an organic crystal made of para-dichlorobenzene. To do this, we use narrow-band continuous-wave<br>lasers and combine spectroscopy methods based on fluorescence excitation and stimulated emission depletion (STED)<br>to select individual vibronic transitions at a resolution of ∼30 MHz dictated by the linewidth of the electronic ex-<br>cited state. In this fashion, we identify several exceptionally narrow vibronic levels in the electronic ground state with<br>linewidths down to values around 2 GHz. Additionally, we sample the distribution of vibronic wavenumbers, relax-<br>ation rates, and Franck-Condon factors, both in the electronic ground and excited states for a handful of individual<br>molecules. We discuss various noteworthy experimental findings and compare them with the outcome of DFT cal-<br>culations. The highly detailed vibronic spectra obtained in our work pave the way for studying the nanoscopic local<br>environment of single molecules. The approach also provides an improved understanding of the vibrational relaxation<br>mechanisms in the electronic ground state, which may help to create long-lived vibrational states for applications in<br>quantum technology.

Spectral splitting of a stimulated Raman transition in a single molecule

Johannes Zirkelbach, Burak Gürlek, Masoud Mirzaei, Alexey Shkarin, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar

The small cross section of Raman scattering has hampered the direct study of this eect at the<br>single molecule level. By exploiting the high Franck-Condon factor of a common-mode resonance,<br>choosing a large vibrational frequency dierence in electronic ground and excited states, and operation<br>at T < 2K, we succeed at driving a coherent stimulated Raman transition in a single molecule.<br>We observe and model a spectral splitting that serves as a characteristic signature of the coherent<br>phenomenon at hand. Our study sets the ground for exploiting the intrinsically ecient coupling<br>of the vibrational and electronic degrees of freedom in molecules for quantum optical operations in<br>the solid state.