University of Warsaw

About: University of Warsaw is a education organization based out in Warsaw, Poland. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 20832 authors who have published 56617 publications receiving 1185084 citations. The organization is also known as: Uniwersytet Warszawski & Warsaw University.

Discrete stages in the solvation and ionization of hydrogen chloride adsorbed on ice particles

Abstract: Ionization and dissociation reactions play a fundamental role in aqueous chemistry. A basic and well-understood example is the reaction between hydrogen chloride (HCl) and water to form chloride ions (Cl(-)) and hydrated protons (H(3)O(+) or H(5)O(2)(+)). This acid ionization process also occurs in small water clusters and on ice surfaces, and recent attention has focused on the mechanism of this reaction in confined-water media and the extent of solvation needed for it to proceed. In fact, the transformation of HCl adsorbed on ice surfaces from a predominantly molecular form to ionic species during heating from 50 to 140 K has been observed. But the molecular details of this process remain poorly understood. Here we report infrared transmission spectroscopic signatures of distinct stages in the solvation and ionization of HCl adsorbed on ice nanoparticles kept at progressively higher temperatures. By using Monte Carlo and ab initio simulations to interpret the spectra, we are able to identify slightly stretched HCl molecules, strongly stretched molecules on the verge of ionization, contact ion pairs comprising H(3)O(+) and Cl(-), and an ionic surface phase rich in Zundel ions, H(5)O(2)(+).

A Transiting Extrasolar Giant Planet around the Star OGLE-TR-10

Abstract: We report a transiting extrasolar giant planet around the star OGLE-TR-10 (orbital period = 3.1 days), which was uncovered as a candidate by the OGLE team in their photometric survey toward the Galactic center. We observed OGLE-TR-10 spectroscopically over a period of 2 yr (2002-2004), using the HIRES instrument with an iodine cell on the Keck I telescope, and measured small radial velocity variations that are consistent with the presence of a planetary companion. This confirms the earlier identification of OGLE-TR-10b by our team and also recently by Bouchy and coworkers as a possible planet. In addition, in this paper we are able to rule out a blend scenario as an alternative explanation. From an analysis combining all available radial velocity measurements with the OGLE light curve, we find that OGLE-TR-10b has a mass of 0.57 ± 0.12MJ and a radius of 1.24 ± 0.09RJ. These parameters bear close resemblance to those of the first known transiting extrasolar planet, HD 209458b.

Structures and Potential Superconductivity in SiH 4 at High Pressure: En Route to “Metallic Hydrogen”

Abstract: A way to circumvent the high pressures needed to metallize hydrogen is to "precompress" it in hydrogen-rich molecules, a strategy probed theoretically for silane. We show that phases with tetrahedral SiH4 molecules should undergo phase transitions with sixfold- and eightfold-coordinate Si appearing above 25 GPa. The most stable structure found can be metallized at under a megabar and at a compression close to the prediction of Goldhammer-Herzfeld criterion. According to a BCS-like estimate, metallic silane should be a high-temperature superconductor.

Abnormal solvent effects on hydrogen atom abstraction. 3. Novel kinetics in sequential proton loss electron transfer chemistry.

Abstract: A prolonged search involving several dozen phenols, each in numerous solvents, for an ArOH/2,2-diphenyl-1-picrylhydrazyl (dpph•) reaction that is first-order in ArOH but zero-order in dpph• has reached a successful conclusion. These unusual kinetics are followed by 2,2‘-methylene-bis(4-methyl-6-tert-butylphenol), BIS, in five solvents (acetonitrile, benzonitrile, acetone, cyclohexanone, and DMSO). In 15 other solvents the reactions were first-order in both BIS and dpph• (i.e., the reactions followed “normal” kinetics). The zero-order kinetics indicate that in the five named solvents the BIS/dpph• reaction occurs by sequential proton loss electron transfer (SPLET). This mechanism is not uncommon for ArOH/dpph• reactions in solvents that support ionization, and normal kinetics have always been observed previously (see Litwinienko, G.; Ingold, K. U. J. Org. Chem. 2003, 68, 3433 and Litwinienko, G.; Ingold, K. U. J. Org. Chem. 2004, 69, 5888). The zero-order kinetics found for the BIS/dpph• reaction in five s...