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  • 1
    Electronic Resource
    Electronic Resource
    Seed Polysaccharides, Gums Separated from Crotalaria Intermedia and Other Leguminous Seeds by Dry Milling (1963)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 11 (1963), S. 317-321 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf60128a013
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  • 2
    Electronic Resource
    Electronic Resource
    Chemical and morphological properties of solution-cast perfluorosulfonate ionomers (1988)
    s.l. : American Chemical Society
    Macromolecules 21 (1988), S. 1334-1339 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00183a025
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  • 3
    Electronic Resource
    Electronic Resource
    An experimental and ab initio investigation of the low-frequency vibrations of coumaran (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 7855-7867 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Coumaran (2,3-dihydrobenzofuran) has been studied using a combination of (1+1′) resonantly enhanced multiphoton ionization (REMPI) and zero electron kinetic energy (ZEKE) studies, supported by ab initio molecular orbital calculations, in order to characterize the low wave number vibrational structure of the S1 neutral excited and D0 ionic ground states. These studies focus primarily on the modifying effects of electronic excitation and ionization on the balance of forces driving the S1 and D0 equilibrium structures toward or away from planarity. The results suggest that coumaran retains a puckered structure in the S1 state, having a barrier significantly smaller than that in the electronic ground state, but is apparently pseudo-planar or weakly puckered in the cation ground state. In each state the drive towards or away from planarity results from a competition between decreasing bond order in the aromatic system which increases torsional interactions thereby favoring a higher barrier and an increase in bond order in the furan ring which has the opposite effect. The lack of symmetry in coumaran lifts any restrictions on which out-of-plane modes can couple, resulting in a rich combination band structure in REMPI and ZEKE spectra, principally involving the ring twisting (44) and the ring pucker (45) vibrational modes. The butterfly mode (43) on the other hand shows surprisingly little activity. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1468315
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  • 4
    Electronic Resource
    Electronic Resource
    Adiabatic and vertical ionization energies of 1,4-diazabicyclo[2,2,2]-octane measured by zero electron kinetic energy spectroscopy and Rydberg extrapolation (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 10560-10571 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have used a combination of high-n Rydberg spectroscopy and zero electron kinetic energy (ZEKE) spectroscopy to measure the adiabatic and vertical ionization energies of 1,4-diazabicyclo[2,2,2]-octane to high precision. A comparison of the two methods revealed that where extended and unperturbed Rydberg series can be observed, the precision with which the ionization energy of a molecule can be measured is up to six times better via Rydberg extrapolation than with high resolution ZEKE spectroscopy. The difference in precision derives, not from any inherent shortcoming in the resolution achievable with ZEKE spectroscopy, but from errors that arise in evaluating the field ionization redshift. Accurate vertical ionization energies of 59 049.0±0.1 and 58 889.9±0.1 cm−1 were obtained for ionization to the 24+1 and 25+1 vibrational levels in the ion. A value for the adiabatic ionization energy of 58 033.3±0.3 cm−1 has been measured by ZEKE spectroscopy for the first time. The precision with which we have been able to account for the field ionization redshift has been improved by calibrating the ZEKE spectrum against the ν25 Rydberg spectrum. The ZEKE spectra presented here were recorded using a double inverted pulse sequence with field strengths as low as 140 mV cm−1. The result was exceptionally well-resolved spectra revealing the rotational contour of each ZEKE band. For the 24+1 and 25+1 bands the spectra revealed a strong central Q branch, with weaker P and R branches, consistent with a propensity for angular momentum transfer to the Rydberg electron rather than within the core. In contrast to what is commonly observed in ZEKE spectroscopy, where rotational autoionization often results in branches associated with negative ΔJ appearing with enhanced intensity, the R branch appears with significantly enhanced intensity compared to the very weak P branch. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1328379
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  • 5
    Electronic Resource
    Electronic Resource
    A study of anthracene–Arn (n=0–5) in the ground cationic state by laser threshold photoelectron spectroscopy: Selective ionization of complex isomers formed in the free jet expansion (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 3429-3441 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The van der Waals complexes formed between anthracene and argon in a free jet expansion are studied using laser resonance enhanced multiphoton ionization (REMPI) threshold photoelectron spectroscopy with the aim of selectively ionizing specific isomers of small- to medium-sized clusters for which discrete absorption peaks exist in the excitation spectrum. Two-color (1+1') REMPI threshold photoelectron spectra of a number of isomers of anthracene–Arn (n=1–5) have been recorded in addition to that of anthracene itself. The following adiabatic ionization energies (Ia) have been obtained to within ±5 cm−1: 59 872 (n=0), 59 807 and 59 825 (n=1), 59 757 and 59 774 (n=2), 59 695 (n=3), 59 606 and 59 660 (n=4), and 59 565 cm−1 (n=5). For n=1–3, detailed van der Waals cation vibrational structure was observed, showing progressions in both bending and stretching mode vibrations. The resulting vibrational information together with the ionization energy red shifts has helped in assigning bands observed in the threshold photoelectron spectra to particular geometric isomers some of which were not necessarily observed in the excitation spectrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466386
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  • 6
    Electronic Resource
    Electronic Resource
    Evidence for spin-orbit autoionization in the zero kinetic energy photoelectron spectrum of molecular iodine ionized via the valence B3.PI.ou+ state (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 16228-16233 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100044a005
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  • 7
    Electronic Resource
    Electronic Resource
    Laser threshold photoelectron spectra of the cis and trans rotational isomers of p-dimethoxybenzene–Arn (n=0,1,2): Observation of the intermolecular van der Waals stretching and bending vibrational modes in the cation (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 4679-4689 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The cis and trans rotational isomers of p-dimethoxybenzene–Arn (n=0,1,2) have been studied in a supersonic free jet by two-color laser resonance enhanced multiphoton ionization threshold photoelectron spectroscopy. The two-color (1+1') threshold photoelectron spectra recorded via the S1 state of the cis and trans isomers of the 1:1 and 1:2 argon complexes reveal well resolved vibrational structure characteristic of the low frequency bending and stretching van der Waals vibrational modes. In the case of the trans isomer of the 1:2 complex, a very low frequency progression (11 cm−1) in a nontotally symmetric van der Waals bending mode appears in single quanta in the spectrum. The equivalent spectrum recorded for the cis isomer exhibits structure characteristic of van der Waals stretching modes as well as double quanta excitation in both totally symmetric and nontotally symmetric van der Waals bending modes. The observation of single quantum excitation in formally forbidden van der Waals vibrational modes implies the possibility of a change in the overall symmetry of the complex in the ground cationic state when compared to that in the S1 state. The adiabatic ionization energies (Ia) for the cis and trans isomers of p-dimethoxybenzene–Arn (n=0,1,2) were measured as 60 774±7 (cis; n=0), 60 687±7 (cis; n=1), 60 509±7 (cis; n=2), 60 563±7 (trans; n=0), 60 479±7 (trans; n=1), and 60 295±7 cm−1 (trans; n=2).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463869
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  • 8
    Electronic Resource
    Electronic Resource
    Vibronic coupling in the ground cationic state of naphthalene: A laser threshold photoelectron [zero kinetic energy (ZEKE)-photoelectron] spectroscopic study (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 7763-7772 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The two-color (1+1') threshold photoelectron spectra of naphthalene in a supersonic free jet have been recorded via nine vibronic levels of the S1 electronic state up to about 1420 cm−1 above the S1 band origin. The threshold photoelectron spectra recorded via the S1 band origin and via totally symmetric ag vibronic levels show significant intensity in Δν=+1 transitions in nontotally symmetric vibrations having b1g symmetry indicating that the ionization transition gains significant intensity through a vibronic coupling mechanism between the two lowest doublet cationic states. The strongest departure from the expected Δν=0 propensity in the threshold photoelectron spectra occurs through excitation of the totally symmetric 8 mode having ag symmetry indicating that a considerable displacement occurs along the normal coordinate of this 8 mode upon ionization from the S1 state. The superior resolution of the threshold photoelectron technique over conventional photoelectron methods has allowed accurate values for the fundamental vibrational frequencies of naphthalene in its ground cationic state to be determined and it has also allowed a more rigorous investigation of the vibronic coupling mechanism that occurs between the two lowest doublet cationic states. Moreover, an improved value for the adiabatic ionization energy of naphthalene of 65 687±7 cm−1 (8.1442±0.0009 eV) has been determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464584
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  • 9
    Electronic Resource
    Electronic Resource
    Observation of torsional motion in the ground-state cation of jet-cooled tolane by two-color threshold photoelectron spectroscopy (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 1649-1654 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High-resolution threshold photoelectron spectra of jet-cooled tolane (C6H5–C≡C–C6H5) have been obtained by two-color (1+1') resonantly enhanced multiphoton ionization via the S1 state {1B1u(ππ*)}. From the threshold photoelectron spectra, the adiabatic ionization energy has been determined to be Ia = 63 917 ± 3 cm−1 (7.9243±0.0004 eV). A vibrational progression due to torsional motion in the cation ground state was observed up to its fifth quantum level with a fundamental frequency of 54 cm−1, showing small anharmonicity. From these results, we have evaluated the potential barrier height to the torsional motion to be 1980±60 cm−1. The threshold photoelectron spectra obtained via several S1 vibronic levels exhibit dominant peaks due to the Δv=0 ionization transitions. This fact indicates that no significant change occurs in molecular structure upon photoionization with removal of the antibonding π electron from the S1 state. Threshold photoelectron bands arising from formally forbidden odd quantum transitions in the torsional mode were also clearly observed with small intensities. The mechanism of the appearance of such a nontotally symmetric mode is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463153
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