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The influence of lateral interactions on the anglular distribution in photodesorption
A375 Surface Science 287/288 (1993) 155-159 North-Holland
Electronic damping of molecular vibrations at metal surfaces: sub-picosecond transient pump-probe spectroscopy Ayao Okiji and Hideaki Kasai Department of Applied Physics, Osaka University, Suita, Osaka 565, Japan Received 1 September 1992; accepted for publication 9 October 1992 A theoretical study is made of the vibrational dynamics of molecules adsorbed on metal surfaces in connection with the sub-picosecond transient pump-probe spectroscopy. The rate equation formalism is used in order to describe the vibrational dynamics in the time domain. The expression for the induced polarization is derived within the rotating-wave approximation. It is shown that in the negative time delay the induced polarization relaxes through the phase and in the positive time delay the induced polarization relaxes through the population within the rate equation formalism. Furthermore, on the assumption that the relaxation mainly proceeds through the coupling of vibrational degrees of freedom to the surface electronic system, the relaxation time involved in the expression for the induced polarization is estimated from a microscopic standpoint. It is shown that the expression for the phase relaxation time is the same as that for the population relaxation time within the Markov approximation.
Surface Science 287/288 (1993) 160-164 North-Holland
The influence of lateral interactions on the angular distribution in photodesorption Hiroyuki Hirayama 1, Arne de Meijere and Eckart Hasselbrink Fritz-Haber-lnstitut der Max-Planck-Gesellschaft, Faradayweg4-6, 1000 Berlin 33, Germany Received 28 August 1992; accepted for publication 24 November 1992 Photodesorption and photodissociation are induced when 0 2 adsorbed on P d ( l l l ) is irradiated with UV light. Both processes are non-thermal. In addition thermal desorption of molecular oxygen is observed as a consequence of a displacement process by the nascent atomic oxygen. Angle-resolved time-of-flight spectra were recorded. For the adsorbed molecular superoxo species these measurements show a pronounced maximum in the translational energy at a desorption angle of 60°. Moreover, this peak is only observed at certain azimuthal angles indicating C3v symmetry.
Surface Science 287/288 (1993) 165-168 North-Holland
Resonance electron scattering by adsorbed molecules: tr* resonance energy versus bond length L. Siller, K.M. Hock, R.E. Palmer Cavendish Laboratory, University of Cambridge, Madingley Roaa~ Cambridge CB3 0HE, UK
and J.F. Wendelken Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA Received 26 August 1992; accepted for publication 19 November 1992 This paper explores the relationship between the energy of the tr* negative ion resonance, observed in the cross-section for vibrational excitation of small molecules in electron energy-loss spectroscopy (EELS), and the intramolecular bond length. On the basis of experimental results assembled from studies of electron scattering by both free and adsorbed molecules containing the C - O group, we find an approximately linear empirical correlation between the resonance energy and the C - O bond length. This correlation is accurately reproduced by multiple-scattering X a calculations for the free CO molecule as a function of bond length, suggesting the possible determination of molecular bond lengths from the or* resonance energies obtained in EELS. Similar calculations are reported for N 2 and 0 2 in addition to CO.
Electronic damping of molecular vibrations at metal surfaces: sub-picosecond transient pump-probe spectroscopy Ayao Okiji and Hideaki Kasai Department of Applied Physics, Osaka University, Suita, Osaka 565, Japan Received 1 September 1992; accepted for publication 9 October 1992 A theoretical study is made of the vibrational dynamics of molecules adsorbed on metal surfaces in connection with the sub-picosecond transient pump-probe spectroscopy. The rate equation formalism is used in order to describe the vibrational dynamics in the time domain. The expression for the induced polarization is derived within the rotating-wave approximation. It is shown that in the negative time delay the induced polarization relaxes through the phase and in the positive time delay the induced polarization relaxes through the population within the rate equation formalism. Furthermore, on the assumption that the relaxation mainly proceeds through the coupling of vibrational degrees of freedom to the surface electronic system, the relaxation time involved in the expression for the induced polarization is estimated from a microscopic standpoint. It is shown that the expression for the phase relaxation time is the same as that for the population relaxation time within the Markov approximation.
Surface Science 287/288 (1993) 160-164 North-Holland
The influence of lateral interactions on the angular distribution in photodesorption Hiroyuki Hirayama 1, Arne de Meijere and Eckart Hasselbrink Fritz-Haber-lnstitut der Max-Planck-Gesellschaft, Faradayweg4-6, 1000 Berlin 33, Germany Received 28 August 1992; accepted for publication 24 November 1992 Photodesorption and photodissociation are induced when 0 2 adsorbed on P d ( l l l ) is irradiated with UV light. Both processes are non-thermal. In addition thermal desorption of molecular oxygen is observed as a consequence of a displacement process by the nascent atomic oxygen. Angle-resolved time-of-flight spectra were recorded. For the adsorbed molecular superoxo species these measurements show a pronounced maximum in the translational energy at a desorption angle of 60°. Moreover, this peak is only observed at certain azimuthal angles indicating C3v symmetry.
Surface Science 287/288 (1993) 165-168 North-Holland
Resonance electron scattering by adsorbed molecules: tr* resonance energy versus bond length L. Siller, K.M. Hock, R.E. Palmer Cavendish Laboratory, University of Cambridge, Madingley Roaa~ Cambridge CB3 0HE, UK
and J.F. Wendelken Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA Received 26 August 1992; accepted for publication 19 November 1992 This paper explores the relationship between the energy of the tr* negative ion resonance, observed in the cross-section for vibrational excitation of small molecules in electron energy-loss spectroscopy (EELS), and the intramolecular bond length. On the basis of experimental results assembled from studies of electron scattering by both free and adsorbed molecules containing the C - O group, we find an approximately linear empirical correlation between the resonance energy and the C - O bond length. This correlation is accurately reproduced by multiple-scattering X a calculations for the free CO molecule as a function of bond length, suggesting the possible determination of molecular bond lengths from the or* resonance energies obtained in EELS. Similar calculations are reported for N 2 and 0 2 in addition to CO.