We have recorded the photoelectron (photodetachment) spectra of the gas-phase negative cluster ions NO−(N2 O)1 and NO−(N2 O)2 using 2.540 eV photons. Both spectra exhibit structured photoelectron spectral patterns which strongly resemble that of free NO−, but which are shifted to successively lower electron kinetic energies with their individual peaks broadened. Each of these spectra is interpreted in terms of a largely intact NO−subion which is solvated and stabilized by nitrous oxide. For both NO−(N2 O)1 and NO−(N2 O)2, the ion–solvent dissociation energies for the loss of single N2 O solvent molecules were determined to be ∼0.2 eV. Electron affinities were also determined and found to increase with cluster size. The localization of the cluster ion’s excess negative charge onto its nitric oxide rather than its nitrous oxide subunit is discussed in terms of kinetic factors and a possible barrier between the two forms of the solvated ion.

We have recorded the photoelectron spectrum of SeO− using a newly constructed negative ion photoelectron spectrometer. The adiabatic electron affinity of SeO is determined to be 1.456±0.020 eV. Values of ν00(a 1Δ–X 3Σ−0+) and ΔG1/2(a 1Δ) are found to be 5530±200 and 916±35 cm−1, respectively, in substantial accord with previous measurements. The negative ion parameters determined in this work are: B″e(SeO−) =0.4246±0.0050 cm−1 which leads to  r′e(SeO−)=1.726±0.010 Å, ω″e(SeO−)=730±25 cm−1, ω′e x″e(SeO−)=2±4 cm−1, and  D0(SeO−)=3.84±0.09 eV. In addition, the spectroscopic parameters of SeO− are compared with those of the electronically analogous negative ions: O−2, SO−, and S−2.

This paper describes a method for fabricating micronozzles using low-temperature wafer-level adhesive bonding with SU-8. The influence of different parameters on the bonding of structured wafers has been investigated. The surface energies of bonded wafers are measured to be in the range of 0.42-0.56 J m −2 , which are comparable to those of some directly bonded wafers. Converging-diverging nozzle structures with throat widths as small as 3.6 µm are formed in an SU-8 film bonded with another SU-8 intermediate layer to produce sealed micronozzles. A novel interconnection technique is developed to interface and test the micronozzles with a macroscopic fluid delivery system to demonstrate the feasibility of the fabrication process. Leakage test results show that this low-temperature wafer bonding process is a viable MEMS fabrication technique for microfluidic applications.

The dominant peaks in the photoelectron spectra of the gas-phase, negative cluster ions H-( NH3)1 and H-( NH3)* provide evidence for describing them as ion-molecule complexes comprised of intact hydride ions which are solvated by ammonia. Vertical detachment energies and approximate ionsingle-solvent dissociation energies are obtained. Other spectral features reveal the complexation-induced distortion of the ammonia solvent( s) by their hydride sub-ions. In the photoelectron spectra of H-(NH3), an additional peak appears which is small and unusually narrow and which does not shift upon deuteration. Evidence is presented for interpreting this peak as arising due to the photodetachment of a tetrahedral isomer of NH, . This previously unknown ammonium anion is not a cluster species, and it is described as a NH; ion core with two Rydberg-like electrons.The study of gas-phase cluster anions provides an avenue for addressing open questions in topics as diverse as ion solvation, excess electrons in fluids, ion-molecule reactions, ion-induced nucleation and electronic band structure in solids. In the past, experimental investigations of negative cluster ions have included thermo~hemical,'-~ kine ti^,^ elec-Tl eV= 1.60218 x low9 J. $The C/A peak intensity ratio increased steadily with decreasing photon energies.

The photoelectron spectra of the gas phase negative cluster ions NH2-(NH3)1 and NH2-(NH3)2 are reported. The spectra imply that these ions consist of intact amide ions solvated by ammonia. Vertical detachment energies and ion-solvent dissociation energies are obtained. In addition, spectral features are also observed that indicate that the ammonia moiety in these cluster anions is distorted from the equilibrium configuration of the free ammonia molecule. The spectra are compared to the photoelectron spectra of H-(NH~)I and H-(NH3)2. Gas phase basicities are determined for N H~-( N H~) I , NH-(NH3)2, H-(NH3),, and H-(NH3)2.While NH2-is a stronger base than H-in the gas phase, our data show that the addition of only two ammonia solvent molecules reverses the relative basicities of these two species. IntroductionThe governing influence of solvation on the energetics, equilibria, and rates of chemical reactions occurring in solution has long been recogni~ed.'-~ There are many cases in which a change in solvent medium changes the rate or equilibrium constant of a reaction by several orders of magnit~de.~ In order to understand solution phase chemistry, a knowledge of the primary reaction chemistry must be supplemented by information on the interactions between reactant and product molecules with the solvent. Distinguishing between the intrinsic properties of reacting chemical species and the effects attributable to solvation, however, is often difficult.The development in the mid-1960s of experimental methods for studying ion-molecule reactions in the gas phase, in the absence of a solvent medium, profoundly influenced our understanding of chemical r e a~t i v i t y .~-~ Using ion cyclotron resonance mass ~pectrometry,~ high-pressure mass spectrometry,* and flowing afterglow methods? it became possible to make thermodynamic and kinetic measurements for a wide variety of chemical reactions without the complicating effects of solvation. Since solvation energies are often large enough to dominate over differences in intrinsic reactivities, the data generated revealed subtle yet important chemical differences for the first time. During the course of these studies, gas phase acid-base chemistry received considerable a t t e n t i~n .~,~. '~-'~ By measuring equilibrium constants for proton transfer reactions, relative acidities and basicities were determined and anchored to an absolute scale (see tables in refs 5, 6, and 16). Of particular significance, it was found that the ordering of relative acidities for a number of alcohols in the gas phase is the reverse of their ordering in s~l u t i o n . '~ Likewise, for a given list of related bases, it was found that the ordering of their basicities in the gas phase often differs from their ordering in s~l u t i o n . '~

We have recorded the phowAeelron spectrum OC P; using a Penning ion source and a negative ion phowAoctron sprc~rome~er. The adinbalic electron arlinily of Pz is determined IO be 0.58920.025 eV. The negalive ion parameters drlermined in this work are: o:(P; ) = 64OA 50 cm-'. R:(P; ) -1.979_tO.O10 A. and D,(P; ) = 4.88f0.06 eV.

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This paper presents a design of lead zirconate titanate (PZT) circular diaphragm actuators to generate large deflections. The actuators utilize a unimorph structure consisting of an active PZT and a passive thermally grown SiO 2 layer. The diaphragm structures were formed by deep reactive ion etching (DRIE). Two different designs, where the PZT layer in the diaphragm actuators was driven by either interdigitated (IDT) electrodes or parallel plate electrodes, were investigated. Both finite element analysis and experimental results proved that the IDT configuration is favorable to generate deflections larger than the diaphragm thickness. The IDT configuration creates an expansion in the PZT layer in the radial direction and a contraction in the tangential direction under forward bias, which enables large deflections. At applied voltages of 100 V, an actuator 800 m in diameter could generate center deflections of around 7.0 m, significantly greater than the diaphragm thickness of 2.8 m. The deflection profiles for the diaphragm actuators became flatter when an inactive region in the annular IDT configuration was introduced. There was also a proportional reduction of the maximum deflection. [1671]Index Terms-Diaphragm, lead zirconate titanate (PZT), microactuator, microelectromechanical systems (MEMS), piezoelectric unimorph.