Ionization of a molecule can greatly alter its electronic structure as well as its geometric structure. In this collaborative experimental and theoretical study, we examined variance in hyperconjugation upon ionization of diethyl ether (DEE) and diethyl sulfide (DES). We obtained the experimental gas phase vibrational spectra of DEE, DES, DEE(+), DES(+), DEE(+)-Ar, and DES(+)-Ar in the wavenumb...

The infrared spectra of substituted chalcones and some of their ferrocene analogues were measured in the region of fundamental and first overtone C = 0 stretching bands. The formation of hydrogen bonds between the substituted chalcones and phenol was examined in the O—H stretching region. The frequencies of fundamental and first overtone C = 0 stretching bands for s-cis and s-trans conformers a...

The first overtones of the stretching and bending vibrations of H2O and the first stretching overtone of D2O were measured to pressures of 37 GPa at 300 K, encompassing the stability fields of water, ice VI, and ice VII. The successive disappearance of the overtone peaks in ice VII with increasing pressure indicates that the barrier height in the double minimum hydrogen potential decreases at a...

We report the first direct observation of the hydrogen-bond stretching vibration for a water cluster. A perpendicular band of ~D2O!3 was measured by terahertz laser vibration–rotation–tunneling spectroscopy at 142.8 cm in the ‘‘translational band’’ region of the liquid corresponding to the hindered translational motions of water molecules. We have tentatively assigned the spectrum to transition...

A comparative study of the resonance Raman spectra of a number of hemoproteins with excitation in the Soret region reveals features that characterize the valence and spin state of the iron. (a) The frequency of the strongest band in the spectra for reduced (ferrous) hemoproteins always occurs between 1356 and 1361 cm-l, whereas for oxidized (ferric) proteins it occurs between 1370 and 1378 cm-l...

We present first-principles calculations for stable and metastable geometries of various hydrogen-related configurations in p-type GaN, including isolated interstitial H as well as Mg-H and Be-H complexes. We also calculate the associated vibrational stretching and wagging modes, systematically including anharmonic contributions to the vibrational frequencies; the anharmonicity is large due to ...

The reorientational motion of the molecules in liquid water is investigated by measuring the anisotropy decay of the O±H stretching mode of HDO dissolved in D2O using femtosecond mid-infrared pump±probe spectroscopy. We observe that the anisotropy shows a non-exponential decay with an initial fast component of which the amplitude increases with increasing lengths of the O±H O hydrogen bond. The...

Quantum mechanical calculations are presented that predict that one-bond deuterium isotope effects on the (15)N chemical shift of backbone amides of proteins, (1)Delta(15)N(D), are sensitive to backbone conformation and hydrogen bonding. A quantitative empirical model for (1)Delta(15)N(D) including the backbone dihedral angles, Phi and Psi, and the hydrogen bonding geometry is presented for gly...

The hydrolysis of adenosine 5'-triphosphate (ATP) at the active site of actin has been studied using density functional calculations. The active site is modeled by the triphosphate tail of ATP, an Mg cation, surrounding water molecules, and the nearby protein residues. Four reaction paths have been followed by constraining coordinates that allow phosphate stretching, nucleophilic attack of the ...