Growth of CO multilayers on the monolayer adsorbate CO/NaCl(100): A high resolution Fourier-transform infrared study

Heidberg, J.; Suhren, M.; Weiß, Helmut

doi:10.1016/0368-2048(93)80083-x

Cited by 15 publications

(12 citation statements)

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“…This is attributed to stochastic growth of the overlayers at 8 K (layer-by-layer growth). [44] For dosing at 13 K, the peaks of the bare monolayer (2154.9 cm −1 ) and the buried monolayer (2153.6 cm −1 ) coexist with varying ratios, depending on the number of overlayers. This is interpreted as the formation of 3D multilayer islands, such that bare monolayer and buried monolayer areas are present at the same time.…”

Section: Structure and Spectroscopy Of Co Adsorbed To Nacl(100)mentioning

confidence: 98%

“…CO overlayers can be grown epitaxially on top of the CO monolayer because the mismatch between the lattice constant of the CO monolayer and that of the CO crystal is small. [43,44] 𝛼-CO shows a cubic crystal structure with the space group symmetry Figure 2.1: Polarized infrared absorption spectra of a 12 C 16 O monolayer on NaCl(100) at an incidence angle of 50°and various temperatures. Reprinted from Ref.…”

Section: Structure and Spectroscopy Of Co Adsorbed To Nacl(100)mentioning

confidence: 99%

“…2.2 (taken from Ref. [44]). Due to the symmetry of the thin slab, the overlayer shows two absorption lines.…”

Section: Structure and Spectroscopy Of Co Adsorbed To Nacl(100)mentioning

confidence: 99%

“…The transverse optical (TO) mode at 2138.9 cm −1 , which is two-fold degenerate, has a transition dipole moment parallel to the surface plane and is thus observed with both s-and p-polarization; the longitudinal optical (LO) mode at 2142.6 cm −1 , which is non-degenerate, has a transition dipole moment perpendicular to the surface and is thus only observed with p-polarization. [44] Figure 2.2: (a) Polarized infrared transmittance spectra of the 12 C 16 O monolayer and 12 C 16 O overlayers at 8 K. The coverages are 1 ML, 1.2 ML, 1.3 ML,3.1 ML 9.3 ML,and 15.6 ML (from top to bottom). Reprinted from Ref.…”

Section: Structure and Spectroscopy Of Co Adsorbed To Nacl(100)mentioning

confidence: 99%

“…Reprinted from Ref. [44], Copyright 1993, with permission from Elsevier. (b) Polarized infrared transmittance spectra of the 12 C 16 O monolayer and 12 C 16 O overlayers at 13 K. The coverages are 1 ML, 3.5 ML,5.8 ML,16 ML,and 125 ML (from top to bottom).…”

Section: Structure and Spectroscopy Of Co Adsorbed To Nacl(100)mentioning

confidence: 99%

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Vibrational Energy Transfer Between CO Molecules on a NaCl(100) Surface Studied by Infrared Fluorescence Spectroscopy

Alexander¹

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The breaking of chemical bonds in surface reactions is inherently connected to highly excited molecular vibrations. Therefore, understanding the vibrational energy transfer dynamics of adsorbed molecules, which effectively determine the lifetime of vibrational excitation, is of great importance. CO adsorbed on NaCl(100) is possibly the best studied physisorbed molecule. Despite that, most previous experiments have focused on the vibrational ground state and the 𝑣 = 0 → 1 transition of CO-mainly because dispersed fluorescence from high vibrational states could not be observed with conventional infrared detectors. In this thesis, I thus investigate the vibrational energy transfer dynamics of CO on NaCl(100) in highly vibrationally excited states up to 𝑣 = 30.Dispersed and time-resolved laser-induced fluorescence (LIF) is used to observe the vibrational dynamics. For this, an improved version of a recently developed mid-infrared emission spectrometer based on superconducting nanowire single-photon detectors (SNSPDs) is used. The current setup is capable of detecting infrared fluorescence from a single adsorbate layer with spectral and temporal resolution of 7 nm and ∼1 µs, respectively. High vibrational states, CO(𝑣), are prepared by pulsed infrared laser excitation of CO to 𝑣 = 1 at cryogenic temperatures around 7 K. Subsequent vibrational energy pooling (VEP), driven by the anharmonicity of the CO oscillators, concentrates many vibrational quanta in single molecules via vibration-to-vibration (V-V) energy transfer from the surrounding molecules: CO(n) + CO(m) → CO(n+1) + CO(m -1).Kinetic Monte Carlo simulations of the vibrational dynamics in a 13 C 18 O monolayer show that VEP proceeds via a sequential mechanism, in which adsorbates in high vibrational states are further excited by collecting vibrational quanta from molecules in lower vibrational states over increasingly large distances and timescales, up to 100 µs. The shape of the phonon spectrum, to which the excess energy in the V-V transfer processes is dissipated, causes a distinct peak structure in the vibrational state distribution. Furthermore, dissipation to transverse phonons that involve Na atom motion in the surface plane is found to be most effective. Vibrational relaxation to the NaCl substrate is slower than VEP and occurs on the millisecond time scale for 𝑣 ≤ 23. The 𝑣-dependent relaxation rates can be explained by a classical electrodynamic mechanism, whereby energy is transferred non-radiatively to the absorbing NaCl medium via the near-field of the oscillating CO dipole. This finding is in strong contrast to the dominating mechanism for more strongly bound adsorbates, where energy is dissipated via anharmonic couplings between the CO vibration and the surface phonons.The improved resolution of the emission spectrometer revealed a previously unknown metastable O-down orientation (Na + -OC), which is formed from the stable C-down v First and foremost, I would like to express my deepest gratitude to my supervisor Alec Wodtke for getting the chance...

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Section: Structure and Spectroscopy Of Co Adsorbed To Nacl(100)mentioning

confidence: 98%

Section: Structure and Spectroscopy Of Co Adsorbed To Nacl(100)mentioning

confidence: 99%

“…2.2 (taken from Ref. [44]). Due to the symmetry of the thin slab, the overlayer shows two absorption lines.…”

Section: Structure and Spectroscopy Of Co Adsorbed To Nacl(100)mentioning

confidence: 99%

Section: Structure and Spectroscopy Of Co Adsorbed To Nacl(100)mentioning

confidence: 99%

Section: Structure and Spectroscopy Of Co Adsorbed To Nacl(100)mentioning

confidence: 99%