1Àx)BaTiO 3 -xBi(Mg 1/2 Ti 1/2 )O 3 [(1Àx)BT-xBMT] polycrystalline ceramics were obtained via solid-state processing techniques. The solubility limit for (1Àx)BT-xBMT was determined to be about x 5 0.07. A systematic structural change from the ferroelectric tetragonal phase to pseudocubic phase was observed at about x ! 0.05 at room temperature. Dielectric measurements revealed a gradual change from normal ferroelectric of pure BaTiO 3 to highly dispersive relaxor-like characteristics in the solid solution with 30-60 mol% Bi(Mg 1/2 Ti 1/2 )O 3 , showing low-temperature coefficients of capacitance over a wide temperature range. The properties of Nb 2 O 5 -doped 0.85BT-0.15BMT ceramics were investigated to better understand the formation mechanism of core-shell structure, for further improving the temperature stability of the dielectric behavior. 1 mol%rxr6 mol%, and (c) 10 molrxr60 mol% calcined at 10001C for 2 h.

We have measured the absolute integral cross sections (σ's) for H3O(+) formed by the reaction of rovibrationally selected H2O(+)(X(2)B1; v1 (+)v2 (+)v3 (+) = 000; N(+) K a (+) K c (+) = 000, 111, and 211) ion with H2 at the center-of-mass collision energy (Ecm) range of 0.03-10.00 eV. The σ(000), σ(111), and σ(211) values thus obtained reveal rotational enhancements at low Ecm < 0.50 eV, in agreement with the observation of the previous study of the H2O(+)(X(2)B1) + D2 reaction. This Communication presents important progress concerning the high-level ab initio quantum calculation of the potential energy surface for the H2O(+)(X(2)B1) + H2 (D2) reactions, which has provided valuable insight into the origin of the rotational enhancement effect. Governed by the charge and dipole-induced-multipole interactions, the calculation shows that H2 (D2) approaches the H end of H2O(+)(X(2)B1) in the long range, whereas chemical force in the short range favors the orientation of H2 (D2) toward the O side of H2O(+). The reorientation of H2O(+) reactant ion facilitated by rotational excitation thus promotes the H2O(+) + H2 (D2) reaction along the minimum energy pathway, rendering the observed rotational enhancement effects. The occurrence of this effect at low Ecm indicates that the long range charge and dipole-induced-multipole interactions of the colliding pair play a significant role in the dynamics of the exothermic H2O(+) + H2 (D2) reactions.

By employing the newly established vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) double quadrupole-double octopole ion guide apparatus, we have examined the translational, rotational, and vibrational energy effects on the chemical reactivity of water cation H2O(+)(X(2)B1) in the collision with deuterium molecule D2. The application of a novel electric-field pulsing scheme to the VUV laser PFI-PI ion source has enabled the preparation of a rovibrationally selected H2O(+)(X(2)B1; v1 (+)v2 (+)v3 (+); N(+) K a+Kc+) ion beam with not only high internal-state selectivity and high intensity but also high translational energy resolution. Despite the unfavorable Franck-Condon factors, we are able to prepare the excited vibrational states (v1 (+)v2 (+)v3 (+))=(100) and (020) along with the (000) ground vibrational state, for collisional studies, where v1 (+), v2 (+), and v3 (+) represent the symmetric stretching, bending, and asymmetric stretching modes of H2O(+)(X(2)B1). We show that a range of rotational levels from N(+) K a+Kc+ = 000 to 322, covering a rotational energy range of 0-200 cm(-1) of these vibrational states, can also be generated for absolute integral cross section (σ) measurements at center-of-mass collision energies (Ecms) from thermal energies to 10.00 eV. The Ecm dependences of the σ values are consistent with the prediction of the orbiting model, indicating that translational energy significantly hinders the chemical reactivity of H2O(+)(X(2)B1). Rotational enhancements are observed at Ecm < 0.30 eV for all the three vibrational states, (000), (100), and (020). While the σ values for (100) are found to be only slightly below those for (000), the σ values for (020) are lower than those for (000) and (100) by up to 20% at Ecm ≤ 0.20 eV, indicative of vibrational inhibition at low Ecm by excitation of the (020) mode. Rationalizations are proposed for the observed rotational enhancements and the bending vibrational inhibition. Rigorous theoretical calculations are needed to interpret the wealth of rovibrationally selected cross sections obtained in the present study.

To understand the dynamics of H3O(+) formation, we report a combined experimental-theoretical study of the rovibrationally state-selected ion-molecule reactions H2O(+)(X(2)B1; v1(+)v2(+)v3(+); NKa(+)Kc(+)(+)) + H2 (D2) → H3O(+) (H2DO(+)) + H (D), where (v1(+)v2(+)v3(+)) = (000), (020), and (100) and NKa(+)Kc(+)(+) = 000, 111, and 211. Both quantum dynamics and quasi-classical trajectory calculations were carried out on an accurate full-dimensional ab initio global potential energy surface, which involves nine degrees of freedom. The theoretical results are in good agreement with experimental measurements of the initial state specific integral cross-sections for the formation of H3O(+) (H2DO(+)) and thus provide valuable insights into the surprising rotational enhancement and vibrational inhibition effects in these prototypical ion-molecule reactions that play a key role in the interstellar generation of OH and H2O species.

Rovibrationally selected ion-molecule collision study using the molecular beam vacuum ultraviolet laser pulsed A vacuum-ultraviolet laser pulsed field ionization-photoelectron study of sulfur monoxide (SO) and its cation (SO +