Deep UV Resonance Raman Spectroscopy with a Tunable 4 kHz Nanosecond Solid-State Laser and a 1 mL Circulating Free-Flow System

Abstract

Abstract Deep UVRR spectra of the aromatic amino acids Phe and Tyr in the wavenumber range 800–1800 cm−1 with λ exc=195–208 nm exhibit a selective enhancement of signals arising from vibrations localized in the aromatic ring. For λ exc>198 nm, the UVRR spectra of Phe and Tyr are dominated by contributions from the in-plane ring stretching modes ν 8a and ν 8b at ∼1600 cm−1. For λ exc≤198 nm, intense signals from the symmetric ring stretching, in-plane C–H bending and phenyl–C stretching vibrations below 1400 cm−1 are observed. Excellent stray light rejection is achieved by a triple monochromator, which can be used either in the additive or subtractive mode for high-resolution and low-wavenumber measurements, respectively. A home-built circulating free-flow system allows the investigation of sample volumes as small as 1 mL.