State-to-state scattering of metastable CO molecules from a LiF (100) surface

Abstract

Scattering of electronically excited, state-selected metastable CO͑a 3 ⌸) molecules from a cleaved LiF͑100͒ surface is studied experimentally. Internal state distributions, fluorescence profiles, time-of-flight ͑TOF͒ profiles and angular distributions of the surviving metastable CO molecules are measured. Relative and absolute survival probabilities are determined for various impact velocities. The dependence of translation and rotational temperature on the velocity of the incoming beam unambiguously indicates a direct inelastic scattering process, even though the angular distributions are broad, both in plane and out of plane. The internal state distribution after scattering shows an overpopulation of the initially prepared ⍀ϭ1-component relative to the other spin components.

State-specific lifetime determination of the a 3Π state in CO

“…1 and has been discussed in detail before. 12,13 A pulsed molecular beam machine, consisting of two differentially pumped vacuum chambers, is connected to an ultrahigh vacuum ͑UHV͒ system. At the end of the UHV system, a 1-m-long flight tube is mounted to increase the flight distance that the molecules can travel.…”

“…12 Although the a→X electric dipole transition is very weak, all molecules will eventually decay back to the electronic ground state via emission of photons in the absence of other deactivation mechanisms. The detection efficiency of this laser induced fluorescence ͑LIF͒ signal depends on the solid angle and the detection volume that can be monitored, as well as on the time that the metastable CO molecules spend in the detection region, i.e., on their velocity.…”

Angular dependence of rotational and vibrational energies of product CO2 in CO oxidation on Pd(110)

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] However, angle-resolved (AR) measurements [6][7][8][9][10][11][12] of internal energies have long been lacking in thermal surface reactions because of the difficulty in conducting such experiments, 18 although such measurements are required in order to obtain detailed structural information. In this paper, results of measurements of internal energies of AR product CO 2 in CO oxidation on Pd (110) are presented.…”

Mode-dependent coupling between vibration and translation of product CO2 in CO oxidation on Pd(111)

“…Dynamics and TS structures can be studied by measurements of translational and internal ͑rotational and vibrational͒ energies of desorbing products. 5,[12][13][14][15][16][17][18][19] Although angle-resolved ͑AR͒ measurements [5][6][7][8][9][10][11] are required to study internal energies to obtain detailed structural information, such measurements have long been lacking in thermal surface reactions because of the difficulty of experiments. In this communication, results of measurements of internal energies of AR product CO 2 in CO oxidation on Pd͑111͒ are presented.…”

“…͓DOI: 10.1063/1.2918729͔ Elucidation of energy transfer dynamics and structures of transition states ͑TSs͒ is an important subject for full understanding of surface reaction. [1][2][3][4][5][6][7][8][9][10][11] Such an understanding at the atomic level is required to develop superior catalysts, electrodes, and material growth processes. Dynamics and TS structures can be studied by measurements of translational and internal ͑rotational and vibrational͒ energies of desorbing products.…”