Search

A study was conducted to examine the transient part of the ion conductivity enhancement in Ca[F.sub.2]/Ba[F.sub.2] heterolayers on annealing at elevated temperatures. The results shed light on the annealed heterolayers that exhibited a strongly increased [F.sup.] conductivity parallel to the interfaces and a substantial but less strong enhancement perpendicular to the interfaces as well as the charge density that remained approximately constant during the annealing process.

A quantitative model for electrochemical Ostwald ripening is presented in which the kinetics is modeled on the level of irreversible thermodynamics for the case that the rate is controlled by the electrode/electrolyte transfer resistance. The kinetic behavior of medium-sized particles and the time dependence of the electromotive force are investigated.

Small mammal traps of 5 types were used for capturing birds during 8 research projects in Massachusetts, Oregon and Washington. Despite relatively high capture rates of birds in Tomahawk and Sherman traps in 2 studies, the 6 other studies had limited avian captures in both these and all other trap types used.

Deals with a study which examined the principles of the analysis and of the preparation strategy for establishing a reproducible defect chemistry at lower temperatures using oxides. Calculation of defect chemistry; Numerical results of electronic and ionic defect concentrations; Technological relevance.

Focuses on a study about the analytical relations of low-temperature defect chemistry of oxides in frozen-in interaction with the ambient oxygen and reversibility of internal interactions, in particular the redistribution of electronic carriers. Ionic and electronic conservation conditions; Way to derive analytical relations describing defect concentrations; Dependencies of defect concentrations on control parameters; Conclusions.

The vibrational predissociation spectrum of the He–HCO+ proton bound complex has been recorded in the 3 μm (C–H stretch) region by monitoring the HCO+ photofragment current. A rotationally resolved, parallel band is observed, red shifted 12.4 cm-1 from the ν1 transition of free HCO+. Analysis in terms of a diatomiclike Hamiltonian yields B″=0.2900±0.0002 cm-1, D″=(1.00±0.06)×10-5 cm-1, B′=0.2898±0.0010 cm-1, and ν1=3076.313±0.010 cm-1. Localized perturbations to ν1 rotational levels are observed and are tentatively ascribed to interactions with combination vibrational states made up of quanta of the CO stretch and HCO+ bend, and those of the low frequency intermolecular stretches and bends. Rotational linewidths are laser bandwidth limited suggesting a lower limit of approximately 250 ps for the lifetime of the ν1 level. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Measurements of total differential cross sections for the scattering of laser-excited K(4 2P3/2) atoms by ground state mercury atoms have been performed in a crossed beam experiment at center-of-mass energies between 0.5 and 6 eV. Characteristic features of the cross section are two well resolved rainbow structures which we can assign to the ∑ and the Π branch of the excited state potential in the scope of the elastic approximation. At energies above 2.1 eV we observe an additional structure in the cross section at large angles which shows the same dependence on the polarization as the amplitude of the ∑ rainbow. This is attributed to a shoulder in the repulsive part of the B ∑ potential. The simultaneously measured differential cross sections for the scattering of K(2S) atoms by mercury have been used to determine the repulsive portion of the ground state potential by inversion, making use of the precisely known well of the potential for this system. [ABSTRACT FROM AUTHOR]

The A 2Π←X 2Π laser-excitation spectra of chloroacetylene and deuterochloroacetylene cations are reported. Analysis of the band systems yields values for all three stretching fundamentals (ν1–ν3) in the excited electronic state. Rotationally resolved spectra of the 000Ω =3/2 subbands have been recorded and analyzed. The derived rotational constants allow estimates of the H–Cl distances in both electronic states to be made. [ABSTRACT FROM AUTHOR]

The rotationally resolved infrared band of the antisymmetric stretching vibration (ν[SUB3]) of N[SUB4,SUP+] has been recorded by tunable diode laser spectroscopy. A continuous supersonic expansion of pure nitrogen through a slit nozzle and electron impact ionization was employed. Forty-four P and R branch transitions with J up to 25 are observed. The band origin is at ν[SUB0] = 2234.5084(4) cm[SUP-1] and the rotational constants are determined to be B[SUB0] = 0.112 05(3) cm[SUP-1] and B[SUB1] = 0.111 76(3) cm[SUP-1]. The infrared spectrum shows that N[SUB4,SUP+] has a linear ground state structure. [ABSTRACT FROM AUTHOR]

Mid-infrared vibrational spectra of He–HN+2 and He2–HN+2 have been recorded by monitoring their photofragmentation in a tandem mass spectrometer. For He–HN+2 three rotationally resolved bands are seen: the fundamental ν1 transition (N–H stretch) at 3158.419±0.009 cm-1, the ν1+νb combination band (N–H stretch plus intermolecular bend) at 3254.671±0.050 cm-1, and the ν1+νs combination band (N–H stretch plus intermolecular stretch) at 3321.466±0.050 cm-1. The spectroscopic data facilitate the development of approximate one-dimensional radial intermolecular potentials relevant to the collinear bonding of He to HN+2 in its (000) and (100) vibrational states. These consist of a short range potential derived from an RKR inversion of the spectroscopic data, together with a long range polarization potential generated by considering the interaction between the He atom and a set of multipoles distributed on the HN+2 nuclei. The following estimates for binding energies are obtained: D0″=378 cm-1 [He+HN+2(000)], and D0′=431 cm-1 [He+HN+2(100)]. While the ν1 band of He2–HN+2 is not rotationally resolved, the fact that it is barely shifted from the corresponding band of He–HN+2 suggests that the trimer possesses a structure in which one of the He atoms occupies a linear proton-bound position forming a He–HN+2 core, to which a second less strongly bound He is attached. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A combined experimental and theoretical study of the structural properties of the H2–HCO+ ion-neutral complex has been undertaken. Infrared vibrational predissociation spectra of mass selected H2–HCO+ complexes in the 2500–4200 cm-1 range display several vibrational bands, the most intense arising from excitation of the C–H and H2 stretch vibrations. The latter exhibits resolved rotational structure, being composed of Σ–Σ and Π–Π subbands as expected for a parallel transition of complex with a T-shaped minimum energy geometry. The determined ground state molecular constants are in good agreement with ones obtained by ab initio calculations conducted at the QCISD(T)/6–311G(2df,2pd) level. The complex is composed of largely undistorted H2 and HCO+ subunits, has a T-shaped minimum energy geometry with an H2...HCO+ intermolecular bondlength of approximately 1.75 Å. Broadening of the higher J lines in the P and R branches of the Π–Π subband is proposed to be due to asymmetry type doubling, the magnitude of which is consistent with the calculated barrier to H2 internal rotation. The lower J lines in the Σ–Σ and Π–Π subbands have widths of 0.06 cm-1, around three times larger than the laser bandwidth, corresponding to a decay time of ≊90 ps for the upper level. The absence of discernible rotational structure in the ν2 band suggests that it has predissociation lifetime of less than 1 ps. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The 9–0 and 9–1 transitions of the A 1Πu–X 1Σ+g system of N2+2 have been observed by fast ion beam photofragment spectroscopy. Multireference configuration interaction ab initio calculations predict v’=8 to be the highest bound level which seemed to be supported by experimental evidence. The dominant predissociation mechanism for the v’=9 level appears to be through tunneling, unlike the v’=6, 7, and 8 levels, which show an e/f symmetry-dependent electronic predissociation. Calculated tunneling lifetimes from our own modified A 1Πu state potential gives good agreement with the experimental lifetimes. In addition to the 9–1 and 9–0 bands, we have also measured the previously unobserved 7–0 and 8–0 rovibronic transitions thus extending Cosby, Müller, and Helm’s study to the blue [Phys. Rev. A 28, 766 (1983)]. Molecular constants have been determined for the v=0 of the X 1Σ+g state and v=7, 8, and 9 of the A 1Πu state. [ABSTRACT FROM AUTHOR]

Spectra of 14N+2–20Ne, 14N+2–22Ne, and 15N+2–20Ne have been recorded in the region of the B 2Σ+u←X 2Σ+g origin transition of N+2. Measurements are made by mass selecting cooled ionic complexes and photodissociating them whilst monitoring the N+2 fragment ion intensity as the laser wavelength is scanned. Various bands are assigned to transitions involving the stretching and bending motions of the Ne...Ne+2 bond with their structure and spacings consistent with transitions between quasilinear geometries in the X and the B states. Spectra of complexes with up to eight neon atoms attached to a 14N+2 core have also been measured. Evidence from shifts of the band origins and analysis of the vibrational frequencies of N+2–Ne2 and N+2–Ne3 suggest a structure where the Ne ligands are sited at one end of the N+2 chromophore. [ABSTRACT FROM AUTHOR]

Vibrationally structured electronic transitions of N2O+–Ar have been observed by measuring the wavelength-dependent yields of the photodissociation reactions to yield N2O+ or Ar+. There appear to be four structured overlapping electronic band systems which are distinguished by vibrational spacings and by their propensity towards production of either N2O+ or Ar+. Variations in the Ar+/N2O+ photoproduct ratio with wavelength are explained as due to vibrational predissociation on different potential-energy surfaces correlating with either Ar+ or N2O+ products. The first band system, observed exclusively at the N2O mass, has its origin close to 445 nm, corresponding approximately to the difference in the energies of N2O+[X 2Π3/2]+Ar[1S0] and N2O[1Σ+]+Ar+[2P3/2] and is assigned as an intracluster charge-transfer transition. Two strong band systems situated to higher energy are assigned as transitions to the two additional electronic states which are expected to correlate with 2P3/2 and 2P1/2 Ar+ and N2O[1Σ+] products. While excitation of these two bands results almost exclusively in Ar+ production, a fourth weaker band near 342 nm leads to N2O+ and appears likely to be a transition to a state correlating with an excited vibronic state of N2O+[A 2Σ+(1,0,0)]+Ar[1S0]. The different band systems exhibit extensive vibrational progressions involving the deformation of the bond between the N2O and the Ar. The shift in the onset of the first charge transfer from the difference in the Ar and N2O ionization potentials combined with the appearance energy for Ar+ production allow tentative estimates of 690 and 1340 cm-1 to be made for the dissociation energies of the lowest and first excited states of N2O+–Ar. [ABSTRACT FROM AUTHOR]

Ionic clusters of nitrogen and helium have been investigated by recording their electronic spectra in the near UV. Structured bands belonging to 14N+2 –He, 14N+2–(He)2, 14N+2–(He)3, and 15N+2 –He have been measured between 390 and 392 nm close to the N+2 B 2Σ+u←X 2Σ+g band origin. Spectra were obtained by exciting mass selected cluster cations with tunable laser radiation and recording the photodissociation cross section as a function of wavelength. The data support the hypothesis that the He– – –N+2 interaction potential has only a small barrier to internal rotation in both the X and B electronic states. A lower estimate for the dissociation energy of the N+2 –He cluster of 101 cm-1 is inferred. [ABSTRACT FROM AUTHOR]

The electronic spectrum of N+2–Ne has been measured in the region corresponding to the B 2∑+u←X 2∑+g origin and 1–0 transitions of N+2. Spectra were obtained by irradiating a mass selected population of N+2–Ne and monitoring the production of N+2 as a function of wavelength. Low temperature N+2–Ne spectra exhibit several well resolved bands. From the shift of the N+2–Ne origin with respect to that of free N+2 it is apparent that the complex dissociation energy D0 is 146.5 cm-1 greater in the B state than the X state. Pronounced changes in the complex’s spectrum occur as the effective temperature is increased. The hottest spectra resemble a broadened and truncated N+2 spectrum. The breaking off at the high energy end of the spectrum at elevated temperatures allows us to establish a rough ground-state dissociation energy of 300 cm-1. Other conclusions resulting from this work are that the equilibrium geometry of the N+2–Ne molecule is probably linear in X and B electronic states, that the ΔG1/2 for the low frequency stretch in the B state is 104 cm-1, and that the N–N stretching motion is affected only very weakly by the presence of the Ne atom. [ABSTRACT FROM AUTHOR]