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  • 1
    Electronic Resource
    Electronic Resource
    Rotational analysis of A˜ 2A1↔X˜ 2E electronic transition of the jet-cooled methylthio radical (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6852-6857 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A set of molecular parameters describing both the X˜ and A˜ states of CH3S, has been obtained by a joint fitting of the rotationally resolved electronic transitions observed in a free-jet-cooled laser-induced fluorescence study of CH3S and an earlier microwave study of its X˜ state. The present work shows that because of incomplete information, nearly all of the previously reported molecular parameters for CH3S must be significantly revised. The present observations show an unusual electronic structure for the radical, characterized by a short C–S bond distance and peculiar methyl group geometry in the ground state. The C–S bond is observed to lengthen markedly in the excited A˜ state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456258
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  • 2
    Electronic Resource
    Electronic Resource
    The multiphoton dissociation of acetylene. I. Long-lived intermediates, sequential and concerted processes of dissociation (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7832-7841 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The multiphoton dissociation processes of acetylene via a two-photon resonant predissociative state, v=0 of 1Σ+g, have been studied by three techniques: time-resolved photofragment excitation spectroscopy (TRPFES), laser-induced fluorescence (LIF) of the C2 fragments, and dispersed emission. We found that the major dissociation products are H atoms, H2 molecules, and C2 molecules in the X 1Σ+g, a 3Πu and A 1Πu states; among the latter, C2 X 1Σ+g molecules are formed by a sequential bond–rupture mechanism whereas some C2 in a 3Πu is formed by a concerted two-bond fission process. Other, minor dissociation channels due to three-photon processes, such as C2(d 3Πg)+2H(2S(1)/(2)), C2(d 3Πg)+H2(X 1Σ+g), C2(C 1Πg)+H2(X), C2(e 3Πg)+H2(X), and C2(D 1Σ+u)+H2(X), were also detected. In the 2+1 concerted dissociation yielding C2(C 1Πg)+H2(X), a long-lived intermediate C2H2, likely a cis isomer or other conformer in which the hydrogen atoms are relatively close to each other, was revealed by TRPFES; its zero-pressure lifetime was estimated to be (8±1) μs. A long-lived intermediate C2H was also found in the 2+1 sequential dissociation by TRPFES.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460118
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  • 3
    Electronic Resource
    Electronic Resource
    Laser spectroscopy of CCH in the 36 600–39 700 cm−1 region (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 1454-1461 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This work reports on nine new bands of the CCH B˜ 2A′←X˜ 2Σ+ system recorded by laser-induced fluorescence. In addition, the 37 946 and 38 107 cm−1 bands were revisited in a supersonic molecular beam. Of these 11 bands, ten were in the 36 600–39 700 cm−1 range; they were rotationally analyzed and assigned as transitions from low vibronic levels, X˜(0,v2,v3) (v2=2–4 and v3=0–1) of CCH to two vibrational levels (T,T+1221) of the B˜ state. Although previously observed as too weak, these bands were enhanced in this work by relaxing vibrationally excited CCH with SF6, instead of He or Ar. The rotationally resolved 35 939 cm−1 band, the band outside of the range of 36 600–39 700 cm−1, is assigned as B˜(T+775)←X˜(0,91,0). These new bands, together with transitions previously reported, are simultaneously analyzed in a nonlinear fit. This work obtained the first spectroscopic parameters of X˜(0,20,0), X˜(0,22,0), X˜(0,22,1), B˜(T+775), and B˜(T+1221), and further improved the spectroscopic parameters of X˜(0,31,0), X˜(0,33,0), and B˜(T). Though the rotational constants of the B˜ state have a very small vibrational dependence, their spin-rotation constants increase by a factor of 2 within 1221 cm−1, suggesting that the B˜ state is perturbed by the nearby unobserved C˜ 2A″ state via the Renner–Teller effect. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479389
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  • 4
    Electronic Resource
    Electronic Resource
    Fluorescence lifetimes and predissociation processes in the B˜ 2A′ state of CCH (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 7394-7399 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Fluorescence lifetimes have been measured under supersonic jet conditions for various N, K-rotational levels of three vibrational levels (T, T+ν2, and T+ν3) of the B˜ 2A′ state of CCH. It was found that the lifetimes of levels T+ν2 and T+ν3 are significantly shorter than that of level T. Furthermore, the lifetimes vary in a complicated way from one rovibronic level to another, indicating the presence of local perturbations. The previously reported CC–H bond energy ranges from 95.6 to 116.3 kcal/mol, which leads to a large uncertainty in assigning the onset of the dissociation process, CCH (X˜ 2Σ+)→C2(X 1Σg+)+H(2S1/2). In this work, fluorescence excitation spectra of photofragment C2 via D 1Σu+←X 1Σg+ and d 3Πg←a 3Πu have been recorded to determine the predissociation processes of the B˜ state. Assuming no barrier is present in the dissociation process of the X˜ and A˜ states, the upper bound of D00(CC–H) was estimated as 39 388±7 cm−1((similar, equals)112.62 kcal/mol). Hence, the lifetime quenching phenomenon observed in the B˜ state is primarily due to predissociation via the dissociative continuum of either the X˜ or the A˜ state of CCH. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481339
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  • 5
    Electronic Resource
    Electronic Resource
    Laser-induced fluorescence spectroscopy of CCH (X˜ 2Σ+) in vibrationally excited levels up to 4500 cm−1 (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 5919-5930 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrationally excited levels of the CCH radical in the X˜ 2Σ+ state up to 4500 cm−1 above the ground vibrational level have been studied both at high pressure and in a supersonic jet by laser-induced fluorescence (LIF). The CCH radical was produced by photolyzing acetylene with 193 nm laser light. Nineteen UV bands are rotationally analyzed and assigned as transitions of parallel type from X˜(0,υl2,υ3), (υ2=0–10, υ3=0–2, l=0–3) to four K sublevels (K=0–3) of a common vibrational level, T, of an upper electronic state most likely B˜ 2A′. Among them, bands at 37 010 and 36 075 cm−1 were previously reported [J. Chem. Phys. 98, 6690 (1993)]; an improved spin–orbit constant of X˜(0,71,0) was determined in this work. Vibrational energies of the l=0 and 1 levels were determined in a simultaneous analysis of UV and IR bands. Assignment of a vibrational level T as the common upper state of the observed LIF bands permits us to determine spectroscopic parameters of the l=2 and 3 levels of the X˜ state, which are reported for the first time. The geometry of level T at 39 157.41 cm−1 is accordingly deduced and agrees with the ab initio prediction of the B˜ state. Our vibrational assignments of the X˜ state, particularly those of bending progressions, are supported by observations of the l=2 and 3 levels. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470472
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  • 6
    Electronic Resource
    Electronic Resource
    Implications of the rotationally resolved spectra of the alkoxy radicals for their electronic structure (1986)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 90 (1986), S. 6766-6769 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100284a011
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  • 7
    Electronic Resource
    Electronic Resource
    193.3 nm photodissociation of acetylene: Nascent state distribution of CCH radical studied by laser-induced fluorescence (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 9153-9161 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The nascent rovibronic distribution of CCH radicals in the 193.3 nm photolysis of acetylene has been measured by laser-induced fluorescence in a supersonic jet. CCH fragments in the X˜ 2Σ+ state are vibrationally hot, but rotationally cold. Predominant CCH fragments were observed at levels of the X˜ state with large mixing of A˜-state character, particularly levels near the potential minimum of A˜ 2Π. This indicates that a nonadiabatic transition near the exit channels plays an important role in the 193.3 nm photodissociation of acetylene. Some, but not all, of the K=1 levels have distinctively bimodal rotational distributions. The relative vibrational energy distributions obtained from this work were used to simulate the translational energy distribution of the hydrogen atom by Balko, Zhang, and Lee [J. Chem. Phys. 94, 7958 (1991)] to extract the population distribution of CCH. It is thus determined that the majority of CCH radicals are formed in the ground electronic state (X˜). Less than half of the CCH population was detected at K=1 levels, and the rest was distributed among K=0, 2, and 3 stacks. The bond energy of HCC–H is estimated as 131.5±0.5 kcal/mol from the vibronic energy of the most populated CCH fragments determined in this work and the translational energy of the recoiled hydrogen atom reported previously by Balko, Zhang, and Lee and Segall, Wen, Lavi, Singer, and Wittig [J. Phys. Chem. 95, 8078 (1991)]. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472763
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  • 8
    Electronic Resource
    Electronic Resource
    The low-lying bending vibrational levels of the CCH (X˜ 2Σ+) radical studied by laser-induced fluorescence (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 6690-6696 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The uv spectrum of the CCH radical was recorded using the laser-induced fluorescence technique on the 193 nm photolysis product of acetylene. Four 2Π–2Π bands at 38 805, 37 946, 37 010, and 36 075 cm−1 of CCH were rotationally analyzed and assigned as transitions from the (0,v21,0) (v2=1, 3, 5, 7) vibrational levels of the X˜ 2Σ+ state to a common upper vibronic state (denoted as U), which possibly belongs to the 2 2Π state. A simultaneous nonlinear least squares fit of the uv bands, in combination with the infrared transitions previously observed in the X˜ 2Σ+ state, provided improved spectroscopic parameters for the U state and the (0,31,0), (0,51,0), and (0,71,0) levels of the X˜ state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464761
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  • 9
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    Laser‐induced fluorescence spectroscopy of CCH (X̃ 2Σ+) in vibrationally excited levels up to 4500 cm−1 (1995)
    American Institute of Physics
    Details
    Publication Date: 1995-10-08
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics
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  • 10
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    A Generic Three-Sided Rearrangeable Switching Network for Polygonal FPGA Design (2013)
    Hindawi
    Details
    Publication Date: 2013-12-12
    Description: We propose a new Polygonal Field Programmable Gate Array (PFPGA) that consists of many logic blocks interconnected by a generic three-stage three-sided rearrangeable polygonal switching network (PSN). The main component of this PSN consists of a polygonal switch block interconnected by crossbars. In comparing our PSN with a three-stage three-sided clique-based (Xilinx 4000-like FPGAs) (Palczewski; 1992) switching network of the same size and with the same number of switches, we find that the three-stage three-sided clique-based switching network is not rearrangeable. Also, the effects of the rearrangeable structure and the number of terminals on the network switch-efficiency are explored and a proper set of parameters is determined to minimize the number of switches. Moreover, we explore the effect of the PSN structure and granularity of cluster logic blocks on the switch efficiency of PFPGA. Experiments on benchmark circuits show that switches and speed performance are significantly improved. Based on experiment results, we can determine the parameters of PFPGA for the VLSI implementation.
    Print ISSN: 1065-514X
    Electronic ISSN: 1563-5171
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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