The potential of the method of fluorescence spectroscopy for the detection of damage and diseases of fruits and vegetables was studied. For this purpose, the spectra of fluorescence of healthy and rotten apples and potatoes have been investigated. Excitation of samples was carried out using a continuous semiconductor laser with a wavelength of 405 nm and a pulsed solid-state laser with a wavelength of 527 nm. Peaks in the region of 600–700 nm in rotten samples were shifted towards shorter wavelengths for most samples in both modes of spectroscopy. The differences in the fluorescence spectra of a healthy and rotten apple surface have been revealed to be in the spectral range of 550–650 nm for 405 nm continuous excitation. When exposed to a laser in a pulsed mode (527 nm), the contribution of the 630 nm peak in the spectrum increases in rotten samples. The observed differences make it possible to use this method for separating samples of healthy and rotten fruits and vegetables. The article paid attention to the influence of many factors such as sample thickness, time after excitation, contamination by soil and dust, cultivar, and location of the probing on fluorescence spectra.

Quantum differences of ortho/para H₂O spin-isomers are considered as a key factor that determines water property taking into account the ortho/para conversion and the unbalanced (1: 1) ortho/para ratio in water. The biophysical mechanism of jump in the permeability of erythrocytes through a microcapillary at 36.6°C in water-based physiological solution and at 37.4°C in heavy water is proposed and discussed.

For the first time, to the best of our knowledge, we demonstrated a new type of Raman laser with asymmetrical cavity at the liquid–air interface. We observed an intriguing stimulated Raman scattering (SRS) threshold dependence when the pumping laser beam waist was transferred through the liquid–air interface, and we demonstrated a paradoxical 30-fold SRS threshold reduction in the vicinity of the water–air surface. The minimum SRS threshold was achieved when the pumping laser beam waist was located at the liquid surface. To explain the abnormal SRS threshold dependence, we suggested a new lasing mechanism. Finally, we demonstrated that threshold measurements at the liquid–air interface are a reliable method to quantitatively measure the interaction length in SRS experiments with a focused beam.

The interaction of laser pulses with tobacco mosaic virus (TMV) in Tris-HCl pH7.5 buffer and in water has been investigated. Ruby laser pulses of 20 ns duration have been used for excitation. The spectrum of the light passing through the sample was registered with the help of a Fabry–Perot interferometer. In the case of TMV in water we observed in the spectrum only one line of the exciting laser light, but for TMV in Tris-HCl pH7.5 buffer a second line appeared, corresponding to stimulated low-frequency Raman scattering (SLFRS) on the breathing radial mode of TMV. The frequency shift of the SLFRS by 2 cm ⁻¹ (60 GHz), the conversion efficiency and the threshold are measured for the first time to the best of our knowledge.

A new calibration procedure, known as mapping conditional-calibration laser-induced breakdown spectroscopy (LIBS), has been suggested to improve analysis results for heterogeneous samples. The procedure is based on LIBS elemental mapping, followed by signal conditioning in every sampling spot to skip signal outliers, then by finalizing the calibration curve construction. The suggested mapping conditional calibration procedure was verified for zinc analysis in soybean grist samples. The laser parameters correspond to those of the hand-held LIBS instrument in order to estimate the influence of sample surface heterogeneity under on-site analysis conditions. The laser spot (60 μm) was equal to or smaller than the typical size of grist particles (40–500 μm) but laser crater dimensions were significantly greater and varied widely (150–450 μm). The LIBS mapping of different spectral signals (atomic and ionic lines for major and minor components) was achieved. Elemental maps were normalized to achieve signal maps that were conditionally spotted to skip signal outliers. It was demonstrated that the suggested mapping conditional-calibration LIBS provided 15 ppm RMSECV for zinc determination in heterogeneous samples, which is typical for agricultural products.