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

16B, 20A/2003G017

Observation of Inner/ Outer-Photoionization of Beryllium Atoms
Fumiko YOSHIDA*1, Leo MATSUOKA1, Ryuta TAKASHIMA1, Hiroyuki OSAKI1, Satoshi
KIKKAWA1, Yu FUKUSHIMA1, Tetsuo NAGATA2, Yoshiro AZUMA3 and Shuichi HASEGAWA1
1The Universityof Tokyo, Bunkyo-Ku, Tokyo 113-8656, Japan
2Meisei
University,Hino, Tokyo 191-8506, Japan
3KEK-PF, Tsukuba, Ibaraki 305-0801, Japan
Introduction
222Following He atom (1s ), Be (1s 2s ) is the next
simplest closed-shell atom. Autoionization of Be atom isimportant process because this phenomenon isconesquence of electron correlation within a relatively
simple system. Therefore detailed theoretical calculations
have carried out using several methods [1]. On the otherhands, few experimental data have existed [2] because thetoxicity of Be as well as the characteristics of law vapor
pressure causes the difficulty of experiment. Then anobservation with high resolution is needed for the purposeof quantitative analysis, which provides valuable
information about autoionization process.
We observed inner-shell photoionization of Be as wellas outer-one and reported measurements about
autoionization-profile of Rydberg states in this paper.
Experiment
The experiment concerning inner-shell photoionizaiton
was performed at BL-16B, while the spectrum ofouter-shell photoionization were measured at BL-20A.
The monochromatized photons interacted with the vaporof Be emerging from electron bombardment oven at about
1100°C. The created photo-ion was detected throughTime of Flight mass spectrometer to distinguish between
singly and doubly charged photo-ions.
Results and Discussion
Inner-shell photoionization
To obtain data with high resolution, we focused on theseveral autoionizing Rydberg series. Consequently, asequence of the inner-shell autoionizing Rydberg series
31were observed, which converge to 1s(2s2p P), 1s(2s2p P),
3
11s(2s3s S) and 1s(2s3s S). Figure 1 shows the spectra of
singly and doubly charged photoionization in the photon
3energy region of 1s(2s2p P)nl Rydberg states. We
identified the resonance belonging to above 4 series, mostof which were observed at the first time in this detailed
investigation. The analysis revealed the autoionization
parameters of resonance energy position E, resonancewidth Γ and Fano parameter q. From the resonanceposition, the energy limits of these 4 series weredetermined using Rydberg formula.
Outer-shell photoionization
Figure 2 shows the spectrum of singly charged
photoionization of Be in the region of 2s double
2excitation. The Rydberg series converging to the 1s 3s

6Users' Report

limit were measured. Another interloper, 1s23p4s, whichis the first member of the 3pns series converging to the21s 3p limit was also observed. It almost overlapped 3s5pstate. The comparison with theoretical calculation
revealed the difference of the profile in the vicinity of21s 3p4s state. That suggests these experimental results
could contribute to the progress of the theory regarding toseries perturbation involved two- electron doubleexcitations.

Figure 1: Be2+ (red line) and Be+ (purple line)
photoionization spectrum with fit curve of Fano profile(blue line) and of Lorentzian distribution (green line).

+Figure 2: Be photoionization spectrum in the region of 2s22excitation. 1s 3snp (n=3-9) Rydberg states and 1s 3p4s
resonance were observed.
References[1] L. Voky et al., Phys. Rev. A46, 3945 (1992), D. –S.
Kim et al., Phys. Rev. A61, 062701 (2000), C. D. Lin etal., Phys. Rev. A51, 1286 (1995).
[2] M. O. Krause et al., Phys. Rev. Lett. 59, 2736 (1987),
R. Wehlitz et al., Phys. Rev. A68, 052708 (2003).
* yoshida@lyman.q.t.u-tokyo.ac.jp