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  • 1990-1994  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Submillimeter wave spectroscopy of XeH+ and XeD+ (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 2352-2360 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The J=0–1 rotational transition of XeH+ and the J=1–2 transition of XeD+, which both occur near 390 GHz, have been studied by microwave absorption spectroscopy. For each of these all nine naturally occurring stable isotopes of xenon were detected. The magnetic hyperfine structure for the 129Xe forms and the electric quadrupole–magnetic hyperfine structure of both 131Xe forms were fully resolved and analyzed to determine the CI and eQq0 constants. The scaled spin–rotation parameter CI/(gIB) is found to be practically identical in XeH+ and HI, as it is also in the isoelectronic pair KrD+ –DBr/HBr. The available magnetic field was too small to resolve the rotational Zeeman effect, but the rotational g factor of XeH+ was estimated from Zeeman broadening. The mass-independent Dunham parameters U01, ΔH01, and ΔXe01 were determined from the very accurate microwave frequencies combined with higher order Dunham coefficients from published Fourier-transform infrared (FTIR) spectroscopy of XeH+ . Although it was not practical to observe XeH+ or XeD+ in excited vibrational states, we were able to detect the J=0–1 (v=1) transition of ArD+ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460941
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Cooper minima and circular dichroism in photoelectron angular distributions (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 7513-7514 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We demonstrate that circular dichroism in photoelectron angular distributions (CDAD), resulting from resonance enhanced multiphoton ionization (REMPI) of an aligned molecular Rydberg state, is a highly sensitive probe of the presence of a Cooper minimum near threshold. To illustrate this application of CDAD, we present the results of ab initio calculations for (1+1') REMPI via the R21(5.5) branch of the D 2Σ+(3pσ) state of NO, where a Cooper minimum is found in l=2 (d wave) of the kπ continuum at a photoelectron kinetic energy of 3.2 eV. The CDAD signal is found to vary rapidly with photoelectron kinetic energy, go through zero, and change sign in the region of the Cooper minimum. This result is predicted by CDAD theory for photoionization from an aligned atomic p orbital.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459377
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The microwave spectrum of PO+: Comparison to SiF+ (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 3504-3510 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave spectrum of PO+ has been detected in discharges in mixtures of PF3, O2, and Ar. Precise frequencies were obtained for 48 rotational transitions in the range 140–470 GHz, including all vibrational states v=0–11. Eight of the lines measured were transitions of P18O+, obtained using 18O2. To fit all of these to a mass independent Dunham expansion, a Watson ΔO01 parameter was required to describe the oxygen isotope shift. From the combined analysis a set of eight mass independent Dunham parameters Ukl and the Dunham potential constants a1–a5 were extracted. Harmonic and anharmonic vibrational constants are obtained from the microwave analysis and compare very well to published results from low resolution emission spectroscopy; the final microwave values of re and ωe are 1.424 992 7(4) A(ring) and 1411.5(3) cm−1. These and the a1–a5 coefficients are in very good agreement with the results of several ab initio calculations we have done on PO+ (and other 22 electron diatomics), including those that were used to define the limits of our initial search for the microwave spectrum of PO+. The vibrational temperature of PO+ in our magnetically enhanced negative glow discharge was found to be very high, near 5500 (500) K. Some additional observations of the microwave spectrum of SiF+, used as a probe of the dynamical and chemical behavior of SiF+ in discharges, are also reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459771
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  • 4
    Electronic Resource
    Electronic Resource
    (2+1') rotationally resolved resonance enhanced multiphoton ionization via the E 2∑+(4s,3d) and H 2∑+(3d,4s) Rydberg states of NO (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 7054-7065 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The results of studies of ionic rotational branching ratios and photoelectron angular distributions resulting from (2+1') resonance enhanced multiphoton ionization of NO via various high J (≈21.5) rotational branches of the E2∑+(4s,3d) and H2∑+(3d,4s) Rydberg states are presented. The rotational branching ratios show the expected ΔN=even rotational propensity rule with very small ΔN=odd signals. The branching ratios for the E2∑+ state are seen to be independent of photoelectron energy with the ΔN=+2 signals strongest and no appreciable higher rotational transfer peaks (||ΔN||≥3). The higher rotational transfer signal for ionization of the H2∑+ state are also negligible but the rotational branching ratios are strongly energy dependent due to a Cooper minimum in the l=3 partial wave of the kσ- and kπ-continua at a photoelectron kinetic energy of 2.6 eV and 2.9 eV, respectively. This leads to a strong rotational selectivity that can be exploited to produce ions in a specific rotational level. These consequences of Cooper minima close to threshold are quite general and their influence on rotational distributions should be readily observable in other molecular systems. The photoelectron angular distributions via both states show a strong energy dependence with a rapid change in the angular distributions around the Cooper minimum associated with the H2∑+ state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459428
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Chemical evidence for ancient beer (1992)
    [s.l.] : Nature Publishing Group
    Nature 360 (1992), S. 24-24 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Lower Mesopotamia, comprising the wide alluvial plain of the lower Tigris and Euphrates rivers, was home to one of the oldest literate civilizations in the world - that of the early Sumerian city-states - dating back to the Late Uruk Period (late fourth millennium BC)1. Irrigation agriculture ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/360024b0
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Contribution to the systematics of r0-derived molecular structure determinations from rotational parameters (1991)
    Springer
    Structural chemistry 2 (1991), S. 581-588 
    Details
    ISSN: 1572-9001
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This work investigates and enumerates the types of molecular structure that can, in principle, be obtained when moments of inertia, planar moments, or rotational constants or different forms of their isotopic differences are least-squares fitted to the respective experimental ground state values. Ther 0-structure, ther 0-derived “pseudo-Kraitchman” structuresr ΔI andr ΔB, and an inequality relation between them are discussed. A least-squares treatment that tries to determine not only the set of structural parameters but also constant, i.e., isotope-independent, rovibrational contributions to the moments of inertia or rotational constants is possible and merits preference. It is shown that the resulting structures are, however, identical with the formerr Δ⌈ orr ΔB-structures, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00673441
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  • 7
    Electronic Resource
    Electronic Resource
    Monolithic integrated active sensors: a combination technology for thin-film and semiconductor devices (1993)
    Springer
    Analog integrated circuits and signal processing 4 (1993), S. 7-20 
    Details
    ISSN: 1573-1979
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract To improve the performance of sensors it is necessary to shrink their physical dimensions. Small sensors can be realized by means of thin-film processes and microlithography. But small sensor dimension implies small output signals. If silicon is used as the substrate for the thin-film device, a possible way out is the monolithic integration of sensor and preamplifying electronics. In this paper we discuss this possibility with respect to an integratedactive thin-film head for high density digital recording. Some important points will be Problems arising from the combination of thin-film and standard semiconductor processes A suitable process flow for the monolithic integration Demands on the electronics for amplifying low-level high-bandwidth signals delivered from thin-film devices with low impedance. Finally we shall present some results achieved with the active thin-film head. The combination technology presented here allows the development of a new generation of “smart sensors.”
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01240675
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