Laser Spectroscopic Determination of theH6eNuclear Charge Radius

Abstract

We have performed precision laser spectroscopy on individual 6He (t(1/2)=0.8 s) atoms confined and cooled in a magneto-optical trap, and measured the isotope shift between 6He and 4He to be 43 194.772+/-0.056 MHz for the 2(3)S1-3(3)P2 transition. Based on this measurement and atomic theory, the nuclear charge radius of 6He is determined for the first time in a method independent of nuclear models to be 2.054+/-0.014 fm. The result is compared with the values predicted by a number of nuclear structure calculations and tests their ability to characterize this loosely bound halo nucleus.

Proton Radius of 14Be from Measurement of Charge-Changing Cross Sections

“…The experimental data are plotted as the filled squares. The errors for 9 Be and 10 Be are greater than those for the other nuclei because of the additional uncertainties in the correction for 8 Be production.…”

“…Assuming that R Ip and the proton rms radius R p are proportional to each other, the ratio Γ=R p /R Ip can be used as a scaling factor. The average value of the ratio for 9 Be, 10 Be, 11 Be, and 12 Be is Γ av =1.142±0.026, where the standard deviation is only about 2%. Next, R p for 14 Be is determined from the measured value of σ cc to be Γ av R Ip ( 14 Be)=2.40±0.07 fm.…”

“…Next, R p for 14 Be is determined from the measured value of σ cc to be Γ av R Ip ( 14 Be)=2.40±0.07 fm. Excluding the data for 9 Be and 10 Be, which have significant errors, from the average, yields Γ av =1.147±0.014. This value is not substantially different but the fluctuation is reduced.…”

“…When the charge-changing cross section (σ cc ) is dominated by geometrical conditions, similar to the case for σ I , it provides information about the proton distribution and the proton radius [17]. Recently, the proton radius for [9][10] Be, [14][15][16] C, and [16][17][18] O isotopes was determined by Yamaguchi et al from σ cc using an empirical scaling law [18]. In this experiment, σ cc's for Be isotopes were measured at approximately 900A MeV.…”

“…The field shift related to the radius can only be obtained by subtracting the theoretical mass shift from the observed value. However, due to recent developments in ISOL techniques [9,10,11,12,13] and in atomic theory [14,15], it has become possible to determine the charge radius for He, Li, and Be isotopes. Nevertheless, it is very difficult to produce nuclei that are far from the stability line, such as 14 Be.…”