The electronic Raman scattering spectrum of PuO₂

Abstract

The Raman spectrum of PuO2 was measured up to 13,000 cm−1 with three different laser excitation wavelengths spanning the resonance (405 nm), near‐resonance (457 nm), and preresonance (514 nm) energy range. Approximately 26 never‐before‐seen bands were observed between 3500 and 13,000 cm−1. Given the very high energy of the Raman shifts of these bands and the relative insensitivity of their spectral position to the interrogating laser wavelength, they are believed to arise from an electronic origin. These bands are present in both freshly calcined and radiolytically aged PuO2, although a broad luminescence is observed in the aged material, which obscures many of the high frequency features. In situ laser annealing of the material attenuated this luminescence and allowed for clear observation of these never‐before‐seen spectral features. Discovery of these high‐energy bands presents a new way of identifying PuO2 for nuclear nonproliferation and forensics purposes.

Spectroscopic analysis of Pu-bearing compounds in double-walled cells

“…Additionally, in the 600 °C-900 °C temperature region, a new set of bands are observed to emerge and sharpen with temperature in the 2,500-2,750 cm −1 spectral region. We believe these bands to be of electronic origin, similar to the electronic bands observed in the Raman spectrum at the 2,135 and 2,635 cm −1 spectral regions (Villa-Aleman et al, 2023b).…”

“…The spectral changes are indicative of the effect of the alpha decay on the crystal lattice. Although the spectral changes are clearly observed in T 2g and the electronic bands at 2,135 (Γ 1 → Γ 5 ) and 2,635 cm −1 (Γ 1 → Γ 3 ), most work follows the T 2g band properties since the band is much narrower than the electronic bands (Villa-Aleman et al, 2021b;Villa-Aleman et al, 2023b).…”

“…The Raman spectrometer used for the work presented here has been described previously (Villa-Aleman et al, 2019a;Villa-Aleman et al, 2019b;Villa-Aleman et al, 2020;Villa-Aleman et al, 2021a;Villa-Aleman et al, 2021b;Christian et al, 2022;Villa-Aleman et al, 2022;Villa-Aleman et al, 2023a;Villa-Aleman et al, 2023b;Christian et al, 2023). In brief, a LabRAM HR800 UV Horiba Jobin-Yvon commercial instrument was used for Raman measurements.…”