Photon Factory Activity Report 2004 #22 Part B (2005)
Chemistry

13C/2003G078

Site-specific ion desorption of fluorinated phthalocyanine
Koji. K. Okudaira1*, Eiichi Kobayashi2, Kazuhiko Mase2, Nobuo Ueno1
1
Faculty of Engineering, Chiba University, 1-33 Yayoi-cyo, Inage-ku, Chiba 263-8522, Japan
2
KEK-PF, Tsukuba, Ibaraki 305-0801, Japan

Experimental
Experiments were performed at the beamline 13C at
the Photon Factory, Institute of Materials Structure
Science. AEPICO spectra were measured by using theEICO apparatus, which is composed of a coaxitiallysymmetric mirror electron energy analyzer and a polarangle-resolved compact time-of-flight ion mass
spectrometer with four concentric anodes. TEY and TIY,Auger, AEPICO spectra were observed at the incidence
angle of the photons of 84º (grazing incidence). TIY andTEY were normalized to the incident photon flux
recorded as the photocurrent at the photon-flux monitor
consisting of a gold-evaporated mesh. All measurements
were performed at room temperature.
Results and discussion+Figure 1 shows AEPICO F signal intensities as afunction of the Ek (AEPICO yield spectra) at hν=691.4 eV(the transition from F 1s to σ(C-F)*) and 695.8 eV. At
these photon energies F 1s NEXAFS spectra show largepeaks. On the other hand, in the total ion yield spectra
the large peak appears only at hν =691.4 eV. In theAEPICO yield spectra at hν=691.4 eV and 695.8 eV, twopeaks appear at Ek=645-650 eV and 620-625 eV. At
hν=691.4 eV, the intensity of the larger Ek peak isremarkably high. The Ek position of this peak in AEPICOyield spectra is about 2 eV larger than that ofcorresponding Auger peak. One the other hand, at hν=695.8 eV, the AEPICO yield is small and the shift is notobserved. The AEPICO peak shift to the Auger peak+indicates that the mechanism of the high F desorption athν = 691.4 eV is related to the spectator-Auger process.

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Users' Report

To estimate the contribution of spectator-Auger process,we compare AEPICO yield spectra with the difference
Auger spectra, because the difference Auger spectra
correspond to the spectator-Auger component. As seen inFig.1, the intense peak positions of the APEICO yield
spectrum at hν=691.4eV is in good agreement with thatof the corresponding difference Auger spectrum. A+
possible explanation of selective F desorption athν=691.4eV is that the desorption is intermediated byspectator-Auger processes.[1] At the final states ofspectator-Auger process C-F bonds are more repulsive
than those at the normal Auger final states, because σ(C+F)* has a C-F antibonding character. The intense F
desorption at the transition F 1s to σ(C-F)* by spectatorAuger process is more effective than that by the normalAuger process.

hν=691.4eV
AEPICO yeld (cps)Introduction
Site-specific chemical bond scission by inner-shell
excitation using synchrotron radiation is a promising
approach to the control of chemical bond scission, since
inner shell excitation is highly localized on specific atoms
in molecules. To clarify the mechanism of ion desorption
induced by inner-shell excitation, the Auger-electron
photo-ion coincidence (AEPICO) method is a powerfultool because it can be used to measure ion desorption
yields for a selected core excitation or a selected
subsequent Auger transition. [1]Recently, for fluorinated copper phthalocyanine+(F16CuPc), selective F desorption occurs by theirradiation of photons corresponding to the transition
from F 1s to σ (C-F)* [2]. In this report we described anion desorption mechanism of F16CuPc by using Auger andAEPICO spectroscopies.

0.50hν=695.8eV

0.05

0600620

640660Auger electron kinetic energy (eV)+Fig 1 F AEPICO spectra at hν=691.4 eV and hν=695.8eV. The solid lines represent the Auger spectra inarbitrary units. The broken lines represent the difference
Auger spectra in arbitrary units.

References[1] K. Mase et al., Low Temperature Phys. 243 29 (2003).
[2] K. K. Okudaira et al., J. Spectrosc. Relat. Phenom.,
137 137-140(2004).
* okudaira@faculty.chiba-u.jp