Photoionization polarization spectroscopy of complex atoms

Abstract

An improved method for the angular momentum measurement of autoionizing levels of complex atoms based on photoionization polarization spectroscopy is reported. In this method, a variation of the ion yield is measured as a function of the combination of the polarizations of the lasers used to excite the autoionizing level through a ladder of intermediate resonant states. Here, eight combinations of different polarizations in three lasers are used, which include not only circular but also linear polarizations. It has been confirmed that the angular momentum of the autoionizing level can be determined uniquely by relative ion-yield measurements for any combination of angular momenta of the levels of the excitation ladders by choosing appropriate intensities of the lasers.

Total angular momenta of even-parity autoionizing levels and odd-parity high-lying levels of atomic uranium

“…In contrast, for higher J states, normally occurring for the middle of the actinide series (e.g. for uranium), a method has been proposed in which one assigns J values by comparing the measured variation pattern with the pattern obtained from the excitation dynamics calculation including the aforementioned factors (Greenland 1988, Greenland et al 1990, Nittoh et al 1994. Unfortunately in the last three papers J values have only been reported for a few AI levels of uranium; this is partly because they used narrow-bandwidth ring dye lasers, with limited accessible wavelength ranges for excitation.…”

Polarization-dependent laser resonance ionization of beryllium

“…The ratio of ion signals at the two polarization conditions is ∼22×. This polarization dependence of ionization efficiency, although reported many times under low atom density conditions such as atomic beams [1][2][3][4][5][6][7][8][9], has now also been observed in the hot-cavity environment of a laser ion source. Therefore laser polarization was proven to be an important operation parameter that deserves attentions for RILIS online beam delivery.…”

“…The radiation diffusion depolarization was theoretically predicted to become important at atomic densities greater than 10 10 cm −3 , and the collisional depolarization at higher concentration [9]. Some previous polarization dependence experiments using atomic beams specifically noted necessary quantitative control on the atom density at 10 8 -10 10 cm −3 to avoid depolarization [5,9]. The observed 2p 2 1 S 0 resonance centers at 76167(6) cm −1 fitted by a Fano profile [18], which is different from the NIST-quoted value of 76190(5) cm −1 [19,20].…”

“…This is particularity significant for the alkaline and alkaline-like element transitions 1 S 0 → 1 P • 1 → 1 S 0 . Due to the polarization relaxation by collisions with environmental atoms, the reported studies of this effect were typically performed on low-density media such as atomic beams [1][2][3][4][5][6][7][8][9], instead of a confined and hot environment like a hot-cavity laser ion source. Initially motivated by the observation of polarization dependence of beryllium (Be) ion yields during online radioactive beam delivery at TRIUMF's isotope separator and accelerator facility (ISAC), a systematic investigation of this effect was performed at the off-line laser ion source test stand (LIS-STAND) [10,11] with atoms in a hot-cavity environment.…”

“…Polarization-based isotopeselective photoionization of palladium and samarium isotopes were preformed [3,4]. This spectroscopic technique was also used to determine the J values in atomic structure studies [5][6][7][8]. All these reported studies were preformed with stable isotope samples and at low atom density -atomic beams.…”