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  • 11
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 7388-7395 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structures of CuX2 (X=Cl and Br) have been investigated in the gas phase by means of anion photodetachment photoelectron spectroscopy and ab initio theory. The photoelectron spectra of CuX2− were recorded at two photon energies, 193 and 157 nm. Well-resolved and rich photodetachment features in the spectra provide unprecedented details for the low-lying electronic states of CuCl2 and CuBr2. The excitation energies for five low-lying electronic states of CuX2 were determined, and they explain well the two previously observed optical absorption bands. The electron affinities for CuCl2 and CuBr2 were determined to be identical, 4.35±0.05 eV within the experimental uncertainty. Both the anions and neutral CuX2 species were calculated to be linear with only a slight bond length variation between the charged and neutral species. The calculated electron affinities and vertical excitation energies for the excited states agree well with the experimental values, yielding a definite assignment for the electronic states of CuCl2 and CuBr2. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 5170-5178 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigated a series of mono-niobium carbide clusters, NbCn− (n=2–7), using anion photoelectron spectroscopy. Vibrationally resolved photoelectron spectra were observed for NbC2− and NbC3−, which were both shown to have cyclic C2v structures. Two isomers were observed for NbC4− and NbC5−. The weak and low electron binding energy isomers were shown to be cyclic structures forming a series with NbC2− and NbC3−, and all have similar and low electron binding energies. The main isomers of NbC4− and NbC5−, which possess much higher electron binding energies, were shown to be due to linear structures, which form a series with NbC6− and NbC7−. All the linear NbCn− clusters were observed to have high electron binding energies and exhibit an even–odd alternation, similar to that observed for pure linear carbon clusters in the same size range. A cyclic to linear structural transition was thus observed for the NbCn− clusters from NbC3− to NbC4−, with the cyclic structures favored for the smaller clusters and the linear isomers favored for the larger clusters. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 10928-10933 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structure of ClOx (x=2–4) radicals were experimentally investigated using anion photoelectron spectroscopy of the respective anions at several photon energies. The electron affinities of ClO3 and ClO4 were obtained for the first time and were found to be very high, 4.25±0.10 and 5.25±0.10 eV, respectively. Three low-lying excited states were observed for ClO2 with excitation energies of 2.10 eV (2B2), ∼2.60 eV (2A1 and 2A2). The 2A1 and 2A2 states were found to be nearly degenerate. Two low-lying states were observed for ClO3 at ∼1.20 eV (2A2) and ∼2.65 eV (2E), whereas no excited state was observed for ClO4 even at our highest photon energy of 157 nm (7.866 eV). The photoelectron spectra were assigned and compared with available theoretical calculations. The excellent agreement between the experimental and theoretical results confirmed the previous calculations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 561-570 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigated free and water-solvated gas phase nitrate anions, NO3−(H2O)n (n=0–6), by photodetachment photoelectron spectroscopy and theoretical calculations. We obtained the electronic structure and electron binding energies of the free and solvated NO3− at three detachment photon energies, 4.661, 6.424, and 7.866 eV. The ground and two low-lying electronic excited states of the NO3 radical (X 2A2′,A 2E″,B 2E′) were observed at the 6.424 and 7.866 eV photon energies. The photoelectron spectra of the solvated nitrate complexes are similar to that of the bare NO3−, except that they become broadened and diffuse due to the solvation. The spectrum of NO3−(H3O)3 showed a resolved vibrational progression of the N–O symmetric stretching (1000 cm−1), suggesting the cluster possesses a high symmetry. NO3− and NO3 were calculated at various levels of theory. Based on the good agreement between density functional theory calculations and experiment for NO3− and NO3, we carried out systematic calculations for NO3−(H2O)n (n=1–6) using primarily density function theory methods. The calculations indicate that NO3−(H2O)n (n=1–3) are all planar, with the first three H2O forming the first solvation shell around NO3−, giving rise to a highly symmetric C3h NO3−(H2O)3. The next three waters form a second solvation shell without direct contact with NO3−. The C3h NO3−(H2O)3 solvation structure was observed to be rather robust and largely preserved in the larger clusters. © 2002 American Institute of Physics.
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  • 15
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 2889-2892 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report a photoelectron spectroscopic study of F−(H2O)n (n=1–4) at 193 and 157 nm. In addition to a detachment feature from F−, we observed a higher binding energy feature in all spectra due to ionization of the solvent molecules leading to F−(H2O)n+ charge-transfer states. Detachment of an electron from F− in F−(H2O) reaches the transition state region of the reaction, F+H2O→HF+OH. The bound to non-bound transition resulted in a long tail at the low binding energy side in the photoelectron spectrum of F−(H2O). We estimated that the neutral F(centered ellipsis)H2O complex at the anion geometry, which is near the transition state region of the H-abstraction reaction, is 6±1 kcal/mol above the F+H2O asymptote, consistent with a previous estimation of a 4 kcal/mol entrance barrier height for this reaction. © 2001 American Institute of Physics.
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  • 16
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 4363-4366 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoelectron spectroscopy of CuO−2 has been studied at three detachment wavelengths: 532 nm, 355 nm, and 266 nm. Vibrationally resolved spectra for two distinct isomers are observed: the Cu(O2) complex and the copper dioxide molecule. The Cu(O)2 complex has an electron affinity (EA) of 1.503 (10) eV with a ground state vibrational frequency of 530 (50) cm−1. Its first electronic excited state is 7400 (300) cm−1 above the ground state. The Cu(O2)− anion is also observed to undergo photodissociation to Cu−+O2 at both 532 nm and 355 nm detachment wavelengths. The copper dioxide molecule is found to have a high EA of 3.46 (4) eV. Three low-lying excited states are observed within 1 eV above the ground state. The first two excited states of the copper dioxide molecule both possess a totally symmetric vibrational frequency of 640 (60) cm−1. © 1995 American Institute of Physics.
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  • 17
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 2701-2707 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoelectron spectra of the title molecules are reported at 3.49 eV photon energy. Vibrational structures are resolved in the spectra of FeC−3 and FeC3H−. The FeC−4 spectrum is unusually broad, indicating a large equilibrium geometry change from the anion to the neutral states. The FeC4H− spectrum exhibits a single strong feature. Theoretical studies using the density functional theory are carried out to determine the structures and bonding of these clusters. All the molecules in the anion ground states are found to be linear with the Fe atom bonded at one end. The Fe and C bonding involves strong Fe 4s and C sp interactions as well as considerable Fe 3d and C π interactions. The n=3 species can be best characterized by cumulenic types of bonding with FeC3H also having an acetylenic isomer. The n=4 species in the linear structures can be approximately described by diacetylenic types of bonding. Mulliken charge analyses indicate that the extra charge in all the anions enters mainly into the Fe 4s antibonding orbital, in agreement with the assignment that the threshold detachment takes place from the σ* orbital mainly between the Fe and C atoms. The vibrational structure resolved in the FeC−3 spectrum yields a Fe–C stretching frequency of 700 (150) cm−1 for the first excited state of FeC3, in agreement with the Fe–C multiple bonding character. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1957-1966 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A magnetic-bottle time-of-flight (TOF) photoelectron spectrometer, coupled with an electrospray ionization source, has been developed for the investigation of multiply charged anions in the gas phase. Anions formed in the electrospray source are guided by a radio-frequency quadrupole ion guide into a quadrupole ion trap, where the ions are accumulated. A unique feature of this apparatus involves the coupling of a TOF mass spectrometer to the ion trap with perpendicular ion extraction. The ion trap significantly improves the duty cycle of the experiments and allows photodetachment experiments to be performed with low repetition-rate lasers (10–20 Hz). This novel combination makes the photodetachment photoelectron spectroscopy studies of multiply charged anions possible for the first time. Furthermore, the perpendicular extraction of ions, pulsed out of the ion trap, to the TOF mass spectrometer allows the ion energies to be conveniently referenced to ground, simplifying the configuration of the TOF mass spectrometer and the subsequent magnetic-bottle TOF photoelectron spectrometer. The mass resolution (M/ΔM) achieved is about 800 for smaller ions. The magnetic-bottle photoelectron spectrometer resolution is about 11 meV full width at half maximum for 0.5 eV photoelectrons with an overall resolution of ΔE/E∼2%. The detailed design, construction, and operation of the new apparatus are presented. © 1999 American Institute of Physics.
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  • 19
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 8389-8395 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrationally resolved photoelectron spectra of MC2− (M=Sc, V, Cr, Mn, Fe, and Co) are reported at two detachment photon energies, 532 and 355 nm. All the spectra showed a well resolved vibrational progression in the ground state detachment features. Electron affinities, vibrational frequencies, and information about the low-lying electronic states were obtained for the first row transition metal dicarbide molecules. The measured electron affinities for the MC2 species show strong metal-dependence with a minimum at VC2 and a maximum at MnC2. The ground state vibrational frequencies were observed to decrease from ScC2 to a minimum in CrC2 and then increases slightly in MnC2 and FeC2. The trends of the electron affinities and vibrational frequencies for the MC2 species were found to correlate well with the corresponding monoxides, suggesting that the chemical bonding in M–C2 is analogous to that in M–O. The M–C2 bonding was thus interpreted to be quite ionic, and MC2 can be qualitatively viewed as M2+C22−, analogous to M2+O2−. © 1999 American Institute of Physics.
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  • 20
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 2464-2469 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoelectron spectra of MoC− and WC− are reported at two detachment energies, 532 and 355 nm. The electron affinities of MoC and WC were measured to be 1.358 (0.010) and 1.022 (0.010) eV, respectively. Seven low-lying electronic states were observed for MoC within 2 eV above its ground state whereas six were observed for WC within 2.4 eV above its ground state. The bonding and spectroscopy of MoC and WC were found to be different and were attributed to their different atomic configurations due to the strong relativistic effects in W. The current study reports the first spectroscopic information on WC. © 1999 American Institute of Physics.
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