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Presents a virtual interface method for extracting growth rates and high temperature optical constants from thin semiconductor films using in situ normal incidence reflectance. Description of the method; Tests using simulations; Experimental verification.

The emission spectrum of Br2 in the ultraviolet (180≤λ≤400nm) has been examined in electron beam pumped rare gas–hydrogen bromide (HBr) gas mixtures. Temporally resolved and rare gas pressure-dependent studies of the Br2 fluorescence at 292 (D’→A’), 312, 334, and 358 nm indicate that the formation processes for Br2 ion pair states differ for Ne and Ar diluents. Experimental evidence suggests that Br2 excited states in the first tier [correlated with Br-(1S0)+Br+(3P2)] in Ar/HBr mixtures are formed by ion–ion recombination in which Br+(3P2) is produced by charge transfer between Ar+(2P) and HBr, followed by predissociation of HBr+(A 2Σ+). In Ne buffer, Br2 states well above D’ are apparently produced by Penning ionization of HBr by Ne 3s 3P followed by recombination of Br+(3P0,1,2 ) ions with Br-(1S0). Also, Ar is effective in collisionally relaxing the lowest manifold of six Br2 ion pair states but both Ne and Ar are poor quenchers of the D’(2g) level. [ABSTRACT FROM AUTHOR]

Absorption from the lowest-lying ion pair state of HgBr (i.e., Hg+–Br-: B 2∑+1/2 ) has been observed by transient absorption spectroscopy in a pulsed, transverse discharge containing a mixture of Ne, N2, and HgBr2 vapor. A highly structured band peaking at ∼447 nm is shown to be associated with charge–transfer transitions from the B 2∑+1/2 state to a higher-lying, covalently bonded (Hg*–Br) state. By pumping the 447 nm transition with a pulsed dye laser while simultaneously monitoring gain on the HgBr (B 2∑+1/2 →X 2∑+1/2 ) band at 502 nm, the absorption cross section for the blue band was measured to be (3.0±1.5)×10-17 cm2 and the saturation intensity for the transition at 447 nm was determined to be 710±50 kW cm-2. [ABSTRACT FROM AUTHOR]

Transient absorption spectra of rare gas dimer Rydberg transitions in the ultraviolet, visible, and near infrared (220≤λ≤900 nm) spectral regions have been observed in electron beam excited rare gases. The most prominent molecular bands for He2, Ne2, Ar2, Kr2, and Xe2 are assigned to the mp 3Πg←ns 3Σ+u (He[ATOTHER]@B:[/ATOTHER]n=2, 3≤m≤10; Ne[ATOTHER]@B:[/ATOTHER]n=3, 4≤m≤10; Ar[ATOTHER]@B:[/ATOTHER]n=4, 5≤m≤15; Kr[ATOTHER]@B:[/ATOTHER]n=5, 6≤m≤16; Xe:n=6, 8≤m≤11) Rydberg series of the dimer. Adiabatic ionization potentials, relative to the ns 3Σ+u state, are determined by extrapolation of the series to their limits (m→∞) to be 34 361.4±30 cm-1 (4.260±0.004 eV) for He2, 34 396.3±25 cm-1 (4.265±0.003 eV) for Ne2, 29 351.9±15 cm-1 (3.639±0.002 eV) for Ar2, 28 428.5±10 cm-1 (3.525±0.001 eV) for Kr2, and 26 664.5±250 cm-1 (3.306±0.031 eV) for Xe2. Absorption bands which are ascribed to m’p 3Σ+g←ns 3Σ+u Rydberg series of Ne2(m’=4,6,8), Ar2(5≤m’≤10), Kr2(6≤m’≤10), and Xe2(m’=8,9) are also reported, and the ns 3Σ+u ionization potentials found to be identical to the respective values quoted above. All of the observed molecular Rydberg states have an A 2Σ+1/2u ion core. The lowest vibrational quanta (ΔG1/2) for the ns 3Σ+u states are determined from vibronic structure in the Rydberg transitions to be 1723 cm-1 for He2, 539 cm-1 for Ne2, 302 cm-1 for Ar2, 172 cm-1 for Kr2, and 135 cm-1 for Xe2, and are consistent with previously reported values. The instability of the ns 3Σ+u metastable state with respect to the dimer ion core potential [D0(A 2Σ+1/2u)-D0(ns 3Σ+u)] is calculated to be 0.508±0.004 eV for He2, 0.681±0.003 eV for Ne2, 0.572±0.002 eV for Ar2, 0... [ABSTRACT FROM AUTHOR]

Rydberg series of Ar2 and Kr2 have been observed in the visible and ultraviolet (350≤λ≤560 nm) absorption spectra of the lowest-lying metastable states of the dimer (ns 3Σ+u(1u, 0-u); Ar: n=4, Kr: n=5). The most prominent series for Ar2 and Kr2 are assigned to ns 3Σ+u → mp 3Πg (Ar: 5≤m≤15; Kr: 6≤m≤16) Rydberg transitions of the diatomic molecule and adiabatic ionization potentials are determined from an extrapolation of the series to their limits (m → ∞) to be 116 356±340 cm-1 (14.43±0.04 eV) for Ar2 and 104 616±150 cm-1 (12.97±0.02 eV) for Kr2. The dissociation energies of the A2Σ+u[1( (1)/(2) )u] dimer ion states of Ar2 and Kr2 are, therefore, 1.33±0.04 and 1.03±0.02 eV, respectively. All of the observed Rydberg states have an A2 Σ+u ion core. Binding energies of the lowest observed 3Πg states, were determined to be (1.331±0.005) eV for Ar2 and (1.030±0.001) eV for Kr2. The quantum defects for the Ar2 and Kr2 series (1.656±0.006 and 2.621±0.004, respectively) and ωe-2ωexe for the ns 3Σ+u metastable state of Ar2 (303±20 cm-1) and Kr2 (172±10 cm-1) were also measured and the vibrational frequencies are consistent with previously reported values. Absorption peaks which are attributed to ns 3Σ+u→m’p 3Σ+g Rydberg transitions of Ar2 (6≤m’≤10) and Kr2 (7≤m’≤10) are also reported. [ABSTRACT FROM AUTHOR]

Presents a study which demonstrated the ultraviolet absorption and photodissociation of As[sub4]. Background on the epitaxy of compound semiconductors using elemental group V sources; Illustration of the experimental apparatus for the arsenic absorption and photolysis experiments; Presentation of the arsenic absorption spectrum.

Reports on a gas phase observation of atomic indium produced by the pyrolysis of trimethylindium in a hydrogen carrier using resonant fluorescence spectroscopy. Importance of understanding the decomposition pathways of the metalorganic precursors used for metalorganic chemical vapor deposition; Details on the decomposition of trimethylindium to indium as a function of susceptor temperature.

BACKGROUND: Use of indwelling urinary catheters can lead to complications, most commonly catheter-associated urinary tract infections. Duration of catheterization is the major risk factor. These infections can result in sepsis, prolonged hospitalization, additional hospital costs, and mortality. OBJECTIVES: To implement and evaluate the efficacy of an intervention to reduce catheter-associated urinary tract infections in a medical intensive care unit by decreasing use of urinary catheters. METHODS: Indications for continuing urinary catheterization with indwelling devices were developed by unit clinicians. For a 6-month intervention period, patients in a medical intensive care unit who had indwelling urinary catheters were evaluated daily by using criteria for appropriate catheter continuance. Recommendations were made to discontinue indwelling urinary catheters in patients who did not meet the criteria. Days of use of a urinary catheter and rates of catheter-associated urinary tract infections during the intervention were compared with those of the preceding 11 months. RESULTS: During the study period, 337 patients had a total of 1432 days of urinary catheterization. With use of guidelines, duration of use was significantly reduced to a mean of 238.6 d/mo from the previous rate of 311.7 d/mo. The number of catheter-associated urinary tract infections per 1000 days of use was a mean of 4.7/mo before the intervention and zero during the 6-month intervention period. CONCLUSIONS: Implementation of an intervention to judge appropriateness of indwelling urinary catheters may result in significant reductions in duration of catheterization and occurrences of catheter-associated urinary tract infections. [ABSTRACT FROM AUTHOR]

The X2Σ+1/2→B2Σ+1/2 absorption band of HgBr has been observed in the afterglow of a pulsed Ne-N2-HgBr2 discharge. Peaking in the ultraviolet (UV) near 350 nm, this continuum degrades slowly to the red and at 410 nm the absorption coefficient is 30% of its maximum value. Upon exciting the X→B band with an XeF (351 nm) or frequency tripled Nd:YAG (355 nm) laser, intense lasing is observed in the blue-green (λ∼502 nm). For λpump=351 nm, the energy conversion efficiency (UV to green) is 22% which corresponds to a photon conversion efficiency of 32%. The quantum efficiency for this four level system is 71%. [ABSTRACT FROM AUTHOR]

Several vibrational bands were observed near 3100 cm[sup -1] in GaN that had been implanted with hydrogen at room temperature and subsequently annealed. Our results indicate that these bands are due to nitrogen-dangling-bond defects created by the implantation that are decorated by hydrogen. The frequencies are close to those predicted recently for V[sub Ga]–H[sub n] complexes, leading us to tentatively assign the new lines to V[sub Ga] defects decorated with different numbers of H atoms. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]