Kiyoshi Ueda

Core Excitation and De-excitation Spectroscopies of Free Atoms and Molecules

This article provides a review of the current status of core excitation and de-excitation spectroscopy studies of free atoms and molecules using a high-resolution soft X-ray monochromator and a high-resolution electron energy analyzer, installed in the soft X-ray photochemistry beam line at SPring-8. Experimental results are discussed for 1s excitation of Ne, O 1s excitation of CO and H 2 O, and F 1s excitation of CF 4 .

Measurements of Oscillator Strengths for the Transitions from the Metastable ^3P Levels of Alkaline-Earth Atoms.II.Magnesium

Oscillator strengths ( f values) for the transitions 3 s 3 p 3 P –3 s n s 3 S ( n =4 and 5), -3 s n d 3 D ( n =4 and 6 to 9) and -3 p 2 3 P in Mg I have been determined by using the hook method. The metastable 3 s 3 p 3 P levels have been populated by a DC discharge of the Mg–He mixture. The absolute scale is based on the absolute f values for 3 s 3 p 3 P –3 s 3 d 3 D (∼0.62). The determined f values are in good agreement with recent theoretical predictions. An estimate of the photoionization cross section from the 3 P levels by extrapolating the f values results in 20.2 Mb at the threshold.

Collision-Induced Dipole Transitions Associated with High-Lying States. : I. Absorption Studies of Barium in Rare Gases

Absorption method has been applied to observe the collision-induced dipole transitions associated with the optically forbidden transitions 6 s 2 1 S 0 -6 p 2 1 D 2 , -6 s 9 d 1 D 2 , -6 s 10 d 1 D 2 , and -5 d 8 p 1 D 2 of barium in argon, krypton or xenon atmosphere. The effective oscillator strength per unit rare-gas density is obtained to be, e.g. , for 6 s 2 -6 s 9 d , 3.6×10 -24 , 2.0×10 -23 , and 5.8×10 -23 cm 3 for argon, krypton, and xenon, respectively. A correlation is found between the effective oscillator strength and the scattering length of the rare-gas atoms for electrons. This is explained from a model in which an adjacent P state mixes into the D state due to the interaction potential between the loosely-bound valence electron and the rare-gas atom.

Oscillator Strengths and Rare-Gas-Induced Broadening of the Principal Series Lines of Ba

Oscillator strengths have been determined for 23 transitions from the ground level of Ba relative to that of the resonance line by the hook method. The results are in good agreement with other experimental values. Rate coefficients of He-, Ar- and Kr-induced broadening have been measured for 6 s 2 1 S 0 -6 s n p 1 P 1 ( n =7 to 10), 6 s 2 1 S 0 -5 d n p 1 P 1 ( n =6 and 7), and 6 s 2 1 S 0 -5 d 7 p 3 D 1 and 3 P 1 by the total absorption method. We find that, generally, the rate coefficient increases monotonously to its maximum value and then decreases with the effective principal quantum number of the upper level relative to the first ionization limit. For 6 s 2 1 S 0 -5 d 7 p 3 P 1 and 3 D 1 , the rate coefficients deviate from this tendency and show minimum values. This singularity is explained qualitatively on the basis of the Fermi potential model by taking account of the configuration mixing.

Collision Broadening of Principal Series Lines of Calcium in the Presence of Krypton

Total absorption method has been applied to 4 s 2 1 S 0 –4 s n p 1 P 1 (6≤ n ≤10) and to 4 s 2 1 S 0 –3 d 4 p 1 P 1 in calcium in the presence of krypton. The determined rate coefficient for Kr-induced broadening increases from 11 to 59×10 -9 cm 3 s -1 as n increases from 6 to 9. This result is reproduced well by a calculation based on a classical broadening theory in which the collision interaction is assumed to be a superposition of the polarization potential and the Fermi potential.

Collision Broadening of Principal Series Lines of Calcium in the Presence of Helium

Total absorption method has been applied to determine broadening rates for 4 s 2 1 S 0 -4 s n p 1 P 1 (6≤ n ≤17) and 4 s 2 1 S 0 -3 d 4 p 1 P 1 in calcium in the presence of helium. A maximum rate coefficient of 1.75×10 -8 cm 3 s -1 occurs for 4 s 2 -4 s 7 p . The admixture of 3 d 4 p configuration with the 1 P 1 series does not induce any marked singularity. The measured rate coefficients are in good agreement with those calculated by the theory of Alekseev and Sobelman for n ≥12, but give larger values by a factor of 2 than those calculated by the theory of Omont for n ≥8. These facts suggest that the inelastic scattering, neglected in the latter theory, contributes considerably to the broadening rates.

Measurement of Oscillator Strengths for Three Lines among the 4s4p 3P-4p2 3P Multiplet of Zn I

The hook method has been applied to the 4 s 4 p 3 P 0 -4 p 2 3 P 1 , 4 s 4 p 3 P 1 -4 p 2 3 P 0 and 4 s 4 p 3 P 2 -4 p 2 3 P 1 transitions at 2079 A, 2097 A and 2104 A as well as to the visible multiplet 4 s 4 p 3 P 0,1,2 -4 s 4 s 3 S 1 at 4680 A, 4722 A and 4811 A. Relative oscillator strengths are determined to be f 2079 / f 4680 * =4.4 ±1.1, f 2097 / f 4722 * =1.5 ±0.4 and f 2104 / f 4811 * =1.3 ±0.4. Uisng known f * values of the visible multiplet the g f values are obtained to be g f 2079 =0.63, g f 2097 =0.63 and g f 2104 =0.90.

Observations of the collision-induced dipole transitions and of a quadrupole transition for barium in krypton

Abstract For Ba perturbed by Kr, collision-induced dipole transitions 6 s 21 S 0 – 6 snd 1 D 2 (8⩽ n ⩽10) have been observed. The effective oscillator strength per unit Kr density was found to be 1.8–1.0 x 10 -23 cm 3 . For the electric-quadrupole transition 6 s 21 S 0 -6 s 6 d 1 D 2 , the oscillator strength is (2.0±0.4) x 10 -6 .

Collision-Induced Dipole Transitions Associated with High-Lying States of Calcium in Rare Gases

Several collision-induced dipole transitions have been observed in the absorption spectra below 2400 A of calcium perturbed by rare gases. The obtained effective oscillator strengths per unit rare gas density are found to correlate with low-energy electron scattering cross sections on the rare-gas atoms.

Rare-Gas-Induced Broadening of Ca Principal Series Lines

We have measured Ar- and Kr-induced broadening of the Ca 4 s 2 1 S -4 s n p (^{1}P (6{leqslant}n{leqslant}10)) and 4 s 2 1 S -3 d 4 p 1 P transitions by means of the total absorption method. In this regime of n , the broadening cross section increases to its maximum value with n and then decreases. The maximum value is 28×10 -14 cm 2 at n =8 for Ar and 72×10 -14 cm 2 at n =9 for Kr. Assuming that the interatomic potential is described as a superposition of the Fermi potential and the polarization potential, we have calculated the cross section on the basis of the classical broadening theory. This calculation agrees well with both the present result and that for the Na 3 S - n S transitions measured by Kachru et al . by means of the trilevel-echo technique.