banner image
No data available.
Please log in to see this content.
You have no subscription access to this content.
No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
Quantum state-resolved gas/surface reaction dynamics probed by reflection absorption infrared spectroscopy
Rent this article for
View: Figures


Image of FIG. 1.
FIG. 1.

Overview of the molecular-beam/surface-science UHV apparatus with FTIR spectrometer and external infrared detector for RAIRS detection.

Image of FIG. 2.
FIG. 2.

Schematic of the molecular beam path including the supersonic expansion nozzle, molecular beam skimmer, chopper disk, pyroelectric detector, beam flag for King & Wells measurements, and the single crystal target surface mounted on a surface science manipulator.

Image of FIG. 3.
FIG. 3.

Relevant dimensions (mm) in the molecular beam path.

Image of FIG. 4.
FIG. 4.

(a) Photographs of the sample holder: (A) Pt(111) single crystal; (B) tungsten heating wires; (C) K-type thermocouples monitor the sample and the holder temperature; (D) copper arm are attached with sapphire spacers (E) to the central dewar assembly (F) filled with liquid nitrogen; (G) heating wire; (H) stainless steel liquid nitrogen cryotube; (b) Pt (111) sample heated to T = 1000 K.

Image of FIG. 5.
FIG. 5.

Detection of vibrationally excited molecules in the molecular beam prepared by IR pumping and detected by a pyroelectric detector. The figure shows the laser power dependence of pyroelectric signal for excitation of CH) originating from the J = 0 and J = 1 rotational states via the R(0) and R(1) transition.

Image of FIG. 6.
FIG. 6.

RAIRS analysis of the CH(ads) uptake on Pt(111) at T = 150 K for an incident molecular beam of 3% CH in (E = 47.7 kJ/mol, T = 700 K): (a) Time evolution RAIRS signals during 80 min molecular beam deposition and (b) final RAIR spectrum after 80 min deposition.

Image of FIG. 7.
FIG. 7.

Calibration of the RAIRS absorption signal CH(ads) at 2281 cm in terms of C coverage on Pt(111) as determined by AES detection. The calibration data indicate a linear relationship between RAIRS absorption signal and CH(ads) coverage with a conversion of θ(CH) [ML] = 211 [ML/abs]. RAIRS + 0.025.

Image of FIG. 8.
FIG. 8.

(a) RAIRS measurement of methyl uptake from a ∼3% CH/He (T = 900 K) molecular beam incident on Pt(111) at a surface temperature of 150 K; the solid line shows the fit of a site-blocking Langmuir uptake model (see text) to the data points to extract the coverage dependent sticking probability S(θ) from the slope of the uptake curve; (b) simultaneous measurement of S(θ) by the King & Wells (K&W) method (a); and (c) comparison of S(θ) measured by RAIRS (a) and K&W (b).

Image of FIG. 9.
FIG. 9.

RAIR spectra of the nascent chemisorption products for the five different methane isotopologues dissociating on Pt (111) at T = 150 K, activated by ∼50 kJ/mol incident translational energy and 5–10 kJ/mol of thermal vibrational excitation from nozzle heating to 700 K. Both C–H and C–D cleavage products are observed for all partially deuterated methane isotopologues. Signals near 2060 cm (defect sites) and 2080 cm (terrace site) are due to a small coverage (≤0.3% ML) of a CO impurity in the molecular beam.

Image of FIG. 10.
FIG. 10.

Initial reactivity for (laser-off •) and (ν state-specific ■) as a function of normal incident translational energy E for dissociative chemisorption of CH on Pt(111) at 150 K. The vibrational efficacy η(υ) ≈ 0.7 is given by the offset between the state-resolved sticking curves (dashed lines) and the vibrational energy of the υ state. Error bars (∼23%) are estimated from the relative errors in the coverage measurements (10%) and in the molecular beam flux measurements (13%).


Article metrics loading...


Full text loading...

This is a required field
Please enter a valid email address
752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Quantum state-resolved gas/surface reaction dynamics probed by reflection absorption infrared spectroscopy