Frequency-resolved high-pressure transient absorption spectroscopy based on a double-chopper configuration.

Dynamics of materials under high-pressure conditions has been an important focus of materials science, especially in the timescale of pico- and femto-second electronic and vibrational motion, which is typically probed by ultrafast laser pulses. To probe such dynamics, it requires an integration of high-pressure devices with the ultrafast laser system. The combination of transient absorption (TA) spectroscopy with diamond anvil cells (DACs) is a novel solution, yet the intense pump scattering light resulting from the small cross section of the DAC may limit the spectral range of the detected signal. In this work, we construct a unique frequency-resolved high-pressure TA spectroscopy system based on a double-chopper configuration, which allows for real-time scattering noise collection and effective elimination. This enables us to freely select the pump wavelength based on the sample's dynamics and obtain complete spectral signals. We test a system with a Rhodamine B solution with the probe wavelength range of 450-750 nm and the 550 nm pump and observe that the intensity of the signal peak corresponding to the monomer at 560 nm continuously decreased relative to the signal peak corresponding to the dimer at 530 nm. This indicates that the portion of Rhodamine B molecules in the dimer form increases under increasing pressure. In addition, we find two dynamic components of the signal peaks for both monomer and dimer: the short-lifetime component increases as the pressure is increased, and the long-lifetime component decreases.