Photon Factory Activity Report 2004 #22 Part B (2005)
Atomic and Molecular Science

2C/2003G159

Resonant Raman scattering in 1s-shell photoionization of N2 molecules
Tatsuji HAYAISHI*1, Satoshi IIZUKA1, Hiroshi YOSHII2, Eigoro MURAKAMI3,
4
Jun-ichi ADACHI , and Akira YAGISHITA4
1
Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
2
Faculty of Medical Science, University of Fukui, Matsuoka, Fukui 910-1193, Japan3
Department of Physics, Chiba Institute of Technology, Narashino, Chiba 275-0023, Japan
4
KEK-PF, Tsukuba, Ibaraki 305-0801, JapanExperimental method
Experiments were carried out at the undulator
beamline BL-2C. The beam line is equipped with agrazing incidence soft X-ray monochromator. A varied
space plane grating with 1000 lines/mm was used. The
spectral resolution of the monochromator with 100µ ×50µ slits was about 0.15 eV at 400 eV photon energy.
Multiply charged ions in coincidence with thresholdelectrons were measured using a time-of-flight mass
spectrometer coupled with a threshold-electron energy
analyzer. The energy resolution of the analyzer wasestimated to be about 0.03 eV.
Results and discussion
Figure 1 shows the yield spectra of N2+, N+ and N++
ions in coincidence with threshold photoelectrons near the
1s-shell photoionization region of N2 molecules. The total
yield spectrum of ions is correspond to thephotoabsorption spectrum, and exhibits some resonancepeaks of 1s-shell photoexcitation. The yield spectrum ofthreshold photoelectrons exhibits a broad and distorted
profile due to post-collision interaction (PCI) [3] near the
1s-shell photoionization threshold, including the someresonance peaks.
These resonance peaks and the PCI profile are reflected++++in the coincidence yield spectra of N2 , N and N , too. It-1
is worth noting that the 1s π* resonance peak at about
401 eV and the profile due to 1s-shell thresholdphotoionization at about 410 eV are dominant in thesecoincidence yield spectra. The PCI profiles in the+++coincidence yield spectra of N and N originate in Auger
decays following 1s-shell threshold photoionization. On+
the other hand, the coincidence yield spectrum of N2

2

Users' Reportexhibits a narrow peak just the 1s-shell photoionizationthreshold of N2. It is conceivable that the peak is due tocontinuous radiative resonant Raman scattering [2].
+Figure 1. Yield spectra of ions, threshold electrons and N2 ,+++
N , N in coincidence with threshold electrons near the10Mion

N2

5M
030k

threshold photoelectron

20k
10k

Counts (288sec)

Introduction
In inner-shell photoionization of atoms and moleculeswith light atomic weight, singly charged ions of atoms
and parent ions of molecules are possibly observed incoincidence with threshold photoelectrons [1]. Normally,
doubly charged ions or more are produced from Augerdecays following inner-shell photoionization. Observationof singly charged ions and parent ions discloses
participation of radiative decays instead of Auger decays.
Namely, the decay process can be expressed as follows,+hν1 + M → M + e (threshold) + hν2 .
This process is the so-called continuous radiative resonant
Raman scattering [2].

0600

N2400+

7.5

2000300+

N

200
1000++

N
1000400

402

404

406

408

410

412

Photon Energy (eV)

1s-shell photoionization region of N2 molecules.
References[1] E. Murakami et al., PF Activity Rep. 20, B, 12 (2002).
[2] T. Åberg and B. Crasemann, “Resonant anomalous Xray scattering” pp. 431-448 (Elsevier Science) (1994).
[3] T. Hayaishi et al., J. Phys. B. 27, L115 (1994).
*hayaishi@bukko.bk.tsukuba.ac.jp