Radiation Damage Mechanisms of Chemotherapeutically Active Nitroimidazole Derived Compounds

Photoionization mass spectrometry, photoelectron-photoion coincidence spectroscopic technique, and computational methods have been combined to investigate the fragmentation of two nitroimidazole derived compounds: the metronidazole and misonidazole. These molecules are used in radiotherapy thanks to their capability to sensitize hypoxic tumor cells to radiation by “mimicking” the effects of the presence of oxygen as a damaging agent. Previous investigations of the fragmentation patterns of the nitroimidazole isomers (Bolognesi et al., 2016; Cartoni et al., 2018) have shown their capacity to produce reactive molecular species such as nitric oxide, carbon monoxide or hydrogen cyanide, and their potential impact on the biological system. The results of the present work suggest that different mechanisms are active for the more complex metronidazole and misonidazole molecules. The release of nitric oxide is hampered by the efficient formation of nitrous acid or nitrogen dioxide. Although both metronidazole and misonidazole contain imidazole ring in the backbone, the side branches of these molecules lead to very different bonding mechanisms and properties

Energy and angular analysis of ejected electrons (6–26 eV) from the autoionization regions of argon at incident electron energies 505 and 2018 eV

High resolution ejected electron spectroscopy has been used to investigate a large number of Ar autoionizing states producing ejected electrons in the energy range from 6 to 26 eV at impact electron energies of 505 and 2018 eV and ejection angles of 40°, 90° and 130°. The full energy range has been divided into three regions which were analyzed separately. In the first one (6–9 eV) the obtained features are identified as the decay of the Ar2+(1D) at 45.11 eV. In the second one (9–14 eV) all features are identified as due to the decay of excited states formed by the excitation of 3s electrons to ns, np and nd subshells. The most prominent features are those arising from the excitation of 3s to nd(3,1D). In this series the 3s3p63d(1D) state with FWHM of 0.040 eV is used as the calibration point for all measured spectra. In the third energy region (14–26 eV) a large number of features is observed. Most of them are identified as the decay of excited states of the type 3s3p5nl and 3s23p4nln′l′

Temperature sensing using YAG:Dy single-crystal phosphor

In this paper, we analyze remote temperature sensing of using dysprosium-doped yttrium aluminum garnet (YAG:$$\hbox {Dy}^{\mathrm {3+}})$$ single crystal by means of fluorescence intensity ratio method. The single crystal was produced by the Verneuil process. Photoluminescence spectra were acquired using continuous laser diode excitation at 365 nm. The calculation of temperature sensing calibration curve was based on ratio of intensities of 458 nm and 493 nm spectral lines. It is shown that the synthesized material can be efficiently used as a thermographic phosphor up to 1273 K. Our results are compared with other recently published results using principal component analysis

Laser-Induced Plasma Measurements Using Nd:YAG Laser and Streak Camera: Timing Considerations

We describe a streak camera system that is capable of both spatial and spectral measurements of laser-induced plasma. The system is based on a Hamamatsu C4334 streak camera and SpectraPro 2300i spectrograph. To improve the analysis of laser-induced plasma development, it is necessary to determine the timing of laser excitation in regard to the time scale on streak images. We present several methods to determine the laser signal timing on streak images—one uses the fast photodiode, and other techniques are based on the inclusion of the laser pulse directly on the streak image. A Nd:YAG laser (λ = 1064 nm, Quantel, Brilliant B) was employed as the excitation source. The problem of synchronization of the streak camera with the Q-switched Nd:YAG laser is also analyzed. A simple modification of the spectrograph enables easy switching between the spectral and spatial measurement modes

Inner shell photofragmentation of 2Cl-pyrimidine studied by mass spectrometry and electron–ion coincidence experiments

Photoelectron spectroscopy, mass spectrometry and electron–ion coincidence experiments combined with tunable synchrotron radiation have been used to study the decay and fragmentation of 2Cl-pyrimidine after Cl(2p), C(1s) and N(1s) excitations. The goal is to investigate how the state- and site-selected excitation and the chemical environment affect the fragmentation paths of the molecule and to make a comparison with fragmentation induced by direct valence ionization. It has been found that the site-selective inner shell excitation affects the branching ratio of the fragments, while the particular fragmentation channels of the cation are determined by the final state populated in the resonant decay of the core excited states. Effects of nuclear motion in the core excited states and the possible ultrafast molecular dissociation following the Cl(2p → σ*) core excitation are discussed

Core shell investigation of 2-nitroimidazole

Tunability and selectivity of synchrotron radiation have been used to study the excitation and ionization of 2-nitroimidazole at the C, N, and O K-edges. The combination of a set of different measurements (X-ray photoelectron spectroscopy, near-edge photoabsorption spectroscopy, Resonant Auger electron spectroscopy, and mass spectrometry) and computational modeling have successfully disclosed local effects due to the chemical environment on both excitation/ionization and fragmentation of the molecule