We measure the absolute frequency of seven out of the nine allowed transitions between the 2(3)S and 2(3)P hyperfine manifolds in a metastable He-3 beam by using an optical frequency comb synthesizer-assisted spectrometer. The relative uncertainty of our measurements ranges from 1 x 10(-11) to 5 x 10(-12), which is, to our knowledge, the most precise result for any optical He-3 transition to date. The resulting 2(3)P-2(3)S centroid frequency is 276 702 827 204.8(2.4) kHz. Comparing this value with the known result for the He-4 centroid and performing ab initio QED calculations of the He-4-He-3 isotope shift, we extract the difference of the squared nuclear charge radii delta r(2) of He-3 and He-4. Our result for delta r(2) = 1.074(3) fm(2) disagrees by about 4 sigma with the recent determination [R. van Rooij et al., Science 333, 196 (2011)].
Frequency Metrology of Helium around 1083 nm and Determination of the Nuclear Charge Radius
Cancio Pastor P;Consolino L;Giusfredi G;De Natale P;
2012
Abstract
We measure the absolute frequency of seven out of the nine allowed transitions between the 2(3)S and 2(3)P hyperfine manifolds in a metastable He-3 beam by using an optical frequency comb synthesizer-assisted spectrometer. The relative uncertainty of our measurements ranges from 1 x 10(-11) to 5 x 10(-12), which is, to our knowledge, the most precise result for any optical He-3 transition to date. The resulting 2(3)P-2(3)S centroid frequency is 276 702 827 204.8(2.4) kHz. Comparing this value with the known result for the He-4 centroid and performing ab initio QED calculations of the He-4-He-3 isotope shift, we extract the difference of the squared nuclear charge radii delta r(2) of He-3 and He-4. Our result for delta r(2) = 1.074(3) fm(2) disagrees by about 4 sigma with the recent determination [R. van Rooij et al., Science 333, 196 (2011)].I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
