In this paper we demonstrate shifted excitation Raman difference spectroscopy (SERDS) for soil analysis as a proof of concept. Confocal Raman microscopy is performed for sample analysis as well as for qualitative comparison with our SERDS experiments. Raman spectra of a soil sample show huge background signals, which mask weak Raman peaks. SERDS clearly separates the Raman signals from background signals with a 10‐fold improvement of the signal‐to‐background noise ratio. Thus, besides hydroxyapatite, additional Raman bands from quartz and feldspar could be extracted. The results demonstrate SERDS as a promising tool for soil analysis. Highlights Raman spectroscopy for soil characterization, e.g., for nutrient management. SERDS as a proof of concept for soil analysis. SERDS extracts Raman signals from disturbing background signals. SERDS as a promising tool for soil investigations.

In this paper, we present a portable shifted excitation Raman difference spectroscopy (SERDS) system applied in outdoor experiments. A dual-wavelength diode laser emitting at 785 nm is used as excitation light source. The diode laser provides two individually controllable excitation lines at 785 nm with a spectral distance of about 10 cm À1 for SERDS. This monolithic light source is implemented into a compact handheld Raman probe. Both components were developed and fabricated in-house. SERDS measurements are performed in an apple orchard, and apples and green apple leafs are used as test samples. For each excitation wavelength, a single Raman spectrum is measured with 50 mW at the sample. Strong background interference from ambient daylight and laser-induced fluorescence obscure the Raman signals. SERDS efficiently separates the wanted Raman signals from the disturbing background signals. For the Raman spectroscopic investigations of green leafs, one accumulation with an exposure time of 0.2 s was used for each excitation wavelength to avoid detector saturation. An 11-fold improvement of the signal-tobackground noise is achieved using SERDS. The results demonstrate the suitability of the portable SERDS system for rapid outdoor Raman investigations.

The complexation of Cm(III) with oxalate is studied in aqueous solution as a function of the ligand concentration, the ionic strength (NaCl), and the temperature (T = 20–90 °C) by time-resolved laser fluorescence spectroscopy (TRLFS) and quantum chemical calculations. Four complex species ([Cm(Ox)n](3–2n), n = 1, 2, 3, 4) are identified, and their molar fractions are determined by peak deconvolution of the emission spectra. The conditional log K′n(T) values of the first three complexes are calculated and extrapolated to zero ionic strength with the specific ion interaction theory approach. The [Cm(Ox)4](5–) complex forms only at high temperatures. Thus, the log K4(0)(T) value was determined at T > 60 °C. The log K1(0)(25 °C) = 6.86 ± 0.02 decreases by 0.1 logarithmic units in the studied temperature range. The log K2(0)(25 °C) = 4.68 ± 0.09 increases by 0.35, and log K3(0)(25 °C) = 2.11 ± 0.05 increases by 0.37 orders of magnitude. The log Kn(0)(T) (n = 1, 2, 3) values are linearly correlated with the reciprocal temperature. Thus, their temperature dependencies are fitted with the linear Van’t Hoff equation yielding the standard reaction enthalpy (ΔrHm(0)) and standard reaction entropy (ΔrSm(0)) of the stepwise formation of the [Cm(Ox)n](3–2n) species (n = 1, 2, 3). Furthermore, the binary ion–ion interaction coefficients of the four Cm(III) oxalate species with Cl(–)/Na(+) are determined. The binding energies, bond lengths, and bond angles of the different Cm(III) oxalate complexes are calculated in the gas phase as well as in a box containing 1000 H2O molecules by ab inito calculations and molecular dynamics simulations, respectively.

The complexation of NpO2+with acetate is studied in aqueous solution by absorption spectroscopy as a function of the total ligand concentration (NaAc), ionic strength (Im= 0.5–4.0 mol kg−1Na+(Cl−/ClO4−)) and temperature (T= 20–85 °C).