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Volumn 1, Issue 1, 2010, Pages 55-61

Vibrational overtone excitation in electron mediated energy transfer at metal surfaces

Author keywords

[No Author keywords available]

Indexed keywords

AU(111) SURFACES; INTRINSIC STRENGTH; KINETIC MODELS; METAL SURFACES; MOLECULAR COLLISIONS; OPTICAL SELECTION RULES; OVERTONE EXCITATION; OVERTONE TRANSITION; QUANTUM JUMPS; SINGLE QUANTUM; STATE-TO-STATE RATE CONSTANTS; STRONG COUPLING; SURFACE TEMPERATURES; THERMALIZATION; VIBRATIONAL EXCITATION; VIBRATIONAL RELAXATION; VIBRATIONALLY EXCITED;

EID: 78650101811     PISSN: 20416520     EISSN: 20416539     Source Type: Journal    
DOI: 10.1039/c0sc00141d     Document Type: Article
Times cited : (29)

References (57)
  • 30
    • 0001252229 scopus 로고
    • 3 with Au(111), but there the mechanism is thought to be purely mechanical in nature. See:
    • 3 with Au(111), but there the mechanism is thought to be purely mechanical in nature. See: B. D. Kay, T. D. Raymond and M. E. Coltrin, Phys. Rev. Lett., 1987, 59, 2792-2794.
    • (1987) Phys. Rev. Lett. , vol.59 , pp. 2792-2794
    • Kay, B.D.1    Raymond, T.D.2    Coltrin, M.E.3
  • 31
    • 79952713298 scopus 로고    scopus 로고
    • note
    • Eqn (2) is derived from the canonical partition function of the simple harmonic oscillator with vibrational frequency n, where h is Planck's constant.
  • 32
    • 79952728402 scopus 로고    scopus 로고
    • note
    • To adapt the model to an anharmonic oscillator would require slight changes where, for example, the statistical factor for 2-1 transitions would be slightly different than for 1-0 transitions.
  • 35
    • 79952722441 scopus 로고    scopus 로고
    • note
    • This turns out to be a practical way to implement the model, but means that the time units are no longer absolute. One may establish absolute time units in a post-facto analysis - vide infra.
  • 37
    • 79952714821 scopus 로고    scopus 로고
    • note
    • 2 was expanded through a piezoelectrically actuated pulsed valve with a stagnation pressure near 3 atm. The valve opening time was ~60 μs. The molecular beam is skimmed and passes through two regions of differential pumping before entering an ultra high vacuum surface science chamber.
  • 38
    • 79952712537 scopus 로고    scopus 로고
    • note
    • 2.
  • 39
    • 79952712804 scopus 로고    scopus 로고
    • note
    • + for at least 30 min and subsequently annealed at 1000 K for at least 30 min. The surface cleanliness was verified using Auger electron spectroscopy. Based on the Auger spectra we estimate the impurities to be below 3% of a monolayer of coverage after sputtering and annealing. Furthermore, we measured before and after scattering and never found evidence for C-building up over the several hours measurement time.
  • 40
    • 79952730937 scopus 로고    scopus 로고
    • note
    • + 1 resonance enhanced multiphoton ionization (REMPI) of NO(n = 1) was accomplished via A-X(0,1) transition using coumarin 480. NO(n = 2) REMPI spectra were recorded via A-X(0,2) transition using coumarin 503, sometimes in a mixture with coumarin 480. NO(n = 0) REMPI spectra, which were necessary for deducing the absolute excitation probabilities were monitored via A-X(0,0) transition, using coumarin 450. The dye laser is pumped with the third harmonic of a Nd:YAG laser. The output of the dye laser was doubled in a BBO crystal.
  • 41
    • 79952711248 scopus 로고    scopus 로고
    • note
    • -1 bandwidth and ~250 nm wavelength.
  • 42
    • 79952730819 scopus 로고    scopus 로고
    • note
    • The ions resulting from REMPI are guided to a two-stage microchannel plate (MCP) detector by a repeller and two electrostatic focusing lenses.
  • 43
    • 79952725214 scopus 로고    scopus 로고
    • note
    • The rotational distributions of scattered NO(n = 0,1,2) were recorded at the peaks of the temporal and angular distributions.
  • 44
    • 79952714297 scopus 로고    scopus 로고
    • note
    • Temporal profiles were recorded by fixing the dye laser's wavelength on a specific rotational line and varying the delay between the laser and molecular beam pulses.
  • 45
    • 79952714304 scopus 로고    scopus 로고
    • note
    • The temporal and angular distributions were independent of the chosen rotational transition.
  • 46
    • 79952725524 scopus 로고    scopus 로고
    • note
    • 00 = 0,1,2) bands after scattering from the surface. These bands were chosen because they are spectrally well isolated. Thus, we may integrate the measured REMPI intensity over the entire rotational distribution of a specific vibrational state. This simplifies the data analysis, eliminating the need to take into account variations of the rotational temperature in the scattered NO that results from changing the surface temperature and/or vibrational state.
  • 47
    • 79952719726 scopus 로고    scopus 로고
    • note
    • The x-axis is the one-photon energy of the 1 + 1 REMPI process.
  • 48
    • 79952722559 scopus 로고    scopus 로고
    • note
    • For measurements of n = 1, a small background was subtracted that arises from rotationally inelastic scattering of thermally populated NO(n = 1) present in the molecular beam. The background level was determined by extrapolating the surface temperature dependence of the NO(n = 1) signal to 0 K using a suitable Arrhenius expression.
  • 49
    • 79952724060 scopus 로고    scopus 로고
    • note
    • Angular and temporal profiles of the scattered NO(n = 0,1,2) were measured for the entire range of surface temperatures used in this work. The 1 + 1 REMPI signal of the scattered NO(n = 0,1,2) was found to vary linearly with the laser intensity (2-4 mJ), The voltage across the MCP was adjusted for each vibrational state with respect to the scattered signal intensity to avoid saturation. The variation of a small scattered signal with the voltage across the MCP detector was measured over the entire range of the MCP voltages used in this work to allow for signal normalization under different detection conditions.
  • 51
    • 79952710366 scopus 로고    scopus 로고
    • The outgoing velocity of the scattered molecules was assumed to be independent of vibrational state. Thus no flux-density correction was performed. See:
    • The outgoing velocity of the scattered molecules was assumed to be independent of vibrational state. Thus no flux-density correction was performed. See: I. Rahinov, R. Cooper, C. Yuan, X. M. Yang, D. J. Auerbach and A. M. Wodtke, J. Chem. Phys., 2008, 129.
    • (2008) J. Chem. Phys. , pp. 129
    • Rahinov, I.1    Cooper, R.2    Yuan, C.3    Yang, X.M.4    Auerbach, D.J.5    Wodtke, A.M.6
  • 52
    • 79952734530 scopus 로고    scopus 로고
    • note
    • The term "culled" refers to a statistical analysis that was carried out on the data to determine if any points are statistical outliers. To accomplish this a canonical fit to the data was carried out and the standard deviation of the fit to the data was determined. Any points that were more that 2.5s from the canonical Arrhenius curve were then eliminated and the canonical fitting was repeated. This process was iterated until all points were within 2.5s of the canonical Arrhenius fit. This resulted in removal of 2 points for the n = 2 data and 5 points for the n = 1 data. If errors were random, points outside 2.5s represent 0.04% of the distribution.
  • 53
    • 0031094626 scopus 로고    scopus 로고
    • Absolute excitation probabilities for NO on Cu(110) appear close to or beyond the thermal limit, possibly reflecting the difficulty of the measurements
    • Absolute excitation probabilities for NO on Cu(110) appear close to or beyond the thermal limit, possibly reflecting the difficulty of the measurements. E. K. Watts, J. L. W. Siders and G. O. Sitz, Surf. Sci., 1997, 374, 191-196.
    • (1997) Surf. Sci. , vol.374 , pp. 191-196
    • Watts, E.K.1    Siders, J.L.W.2    Sitz, G.O.3
  • 54
    • 79952718163 scopus 로고    scopus 로고
    • note
    • The root mean square deviation of the fit was minimized by hand.
  • 55
    • 79952733056 scopus 로고    scopus 로고
    • note
    • The 1/e time to equilibrium can be found easily and is ~700 fs.
  • 57
    • 79952723686 scopus 로고    scopus 로고
    • note
    • The pre-factor, A, is related to the channel specific coupling of molecular vibration to EHPs. In a soon to be published paper, we will present simple analytical expressions for the Arrhenius constants in terms of the fundamental parameters of the kinetic model of this paper.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.