Research
The Keefer group’s general paradigm is to theoretically design and predict novel means to measure and manipulate molecular motion with light.
Ultrafast Spectroscopy
We simulate the spectroscopic interrogation of molecular dynamics with ultrashort laser pulses. In analogy to a video camera, stroboscopic frames of information are concatenated to form a “molecular movie”. Our goal is to theoretically conceptualize movies that have not yet been recorded. A focus is on X-ray sources from free-electron lasers and high harmonic generation setups, which provide unprecedented temporal, spectral and spatial resolution. We actively collaborate with experimental groups to find practical ways to realize our ideas and to provide interpretations for cutting-edge measurements.
Key achievements
| Developed polarized X-ray coherent Raman to separate vibrational from electronic coherences in molecular dynamics | V. Erić, ..., DK*, submitted (2026) |
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| Developed heterodyne-detected four wave mixing for quantum state tomography of vibronic coherences | P. Rupprecht, F. Montorsi,..., DK*, and S. Leone, Phys. Rev. Lett. 2025 |
| Demonstrated how coherent spectroscopic information can be recovered from noisy X-ray sources in a covariance approach | S. Cavaletto, DK et el., Phys. Rev. X 2021 |
| Discovered direct signatures from conical intersections in gas-phase X-ray diffraction of molecules | DK et al., Proc. Natl. Acad. Sci 2021 |
| Demonstrated how X-ray Raman spectroscopy can visualize coherence maps (fingerprints) of conical intersections in molecular photorelaxationEmpty | DK et al., Proc. Natl. Acad. Sci. 2020 |