Dissociative x-ray lasing.

X-ray lasing is predicted to ensue when molecules are pumped into dissociative core-excited states by a free-electron-laser pulse. The lasing is due to the population inversion created in the neutral dissociation product, and the process features self-trapping of the x-ray pulse at the gain ridge. Simulations performed for the HCl molecule pumped at the 2p(1/2)→6σ resonance demonstrate that the scheme can be used to create ultrashort coherent x-ray pulses.

A convenient and efficient protocol for the synthesis of 5-aryl-1,3-diphenylpyrazole catalyzed by hydrochloric acid under ultrasound irradiation.

The synthesis of 5-aryl-1,3-diphenylpyrazole via the reactions of 3-aryl-2,3-epoxy-1-phenyl-1-propanone with phenylhydrazine was carried out in 69-99% yields at room temperature under ultrasound irradiation. This method provides several advantages such as operational simplicity, higher yield and environment friendly.

Atomic polarization in the photodissociation of diatomic molecules.

The angular momentum polarization of atomic photofragments provides a detailed insight into the dynamics of the photodissociation process. In this article, the origins of electronic angular momentum polarization are introduced and experimental and theoretical methods for the measurement or calculation of atomic orientation and alignment parameters described. Many diatomic photodissociation systems are surveyed, in order to provide an overview both of the historical development of the field and of the most state-of-the-art contemporary studies.

The use of capillary gas chromatography-mass spectrometry for identification of radiation-induced DNA base damage and DNA base-amino acid cross-links.

Application of capillary gas chromatography-mass spectrometry (GC-MS) to isolation and identification of radiation-induced DNA base damage including DNA base-amino acid crosslinks is reported. gamma-Irradiated samples of thymine (thy), thymidine (dT), thymidine-5'-monophosphate (pdT), cytosine(cyt),2'-deoxycytidine (dC), 2'-deoxycytidine-5'-monophosphate (pdC), and mixtures of thy, dT and pdT with tyrosine were used as model systems. Trimethylsilylation was used as the derivatization method. Samples containing nucleosides and nucleotides were first subjected to hydrolysis with formic acid or hydrochloric acid to remove sugar or sugar-phosphate moieties, then trimethylsilylated and analyzed by GC-MS. Trimethylsilyl derivatives of radiation-induced monomeric and dimeric products of the model systems mentioned above were shown to have excellent GC properties and easily interpretable mass spectra. The presence of the molecular ion (M+.) and a characteristic (M-CH3)+ ion in the mass spectra facilitated structural elucidation. The complementary use of tert.-butyldimethylsilyl derivatives was also demonstrated. These derivatives provided an intense characteristic (M-57)+ ion in their mass spectra, which may be used to corroborate the molecular weight and to monitor the corresponding compounds in a complex mixture by means of selected-ion monitoring. All gas chromatograms and mass spectra obtained are discussed in detail.