Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userHigh-precision measurement and ab initio calculation of the $(6s^26p^2),^3!P_0 rightarrow , ^3!P_2$ electric quadrupole transition amplitude in $^{208}$Pb
45
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We have completed a measurement of the $(6s^26p^2), ^3!P_0 rightarrow , ^3!P_2$ 939 nm electric quadrupole ($E2$) transition amplitude in atomic lead. Using a Faraday rotation spectroscopy technique and a sensitive polarimeter, we have measured this very weak $E2$ transition for the first time, and determined its amplitude to be $langle ^3!P_2 || Q || ^3!P_0 rangle$ = 8.91(9) a.u.. We also present an ab initio theoretical calculation of this matrix element, which agrees with experiment at the 0.5% level. We heat a quartz vapor cell containing $^{208}$Pb to between 800 and 940 $^{circ}$C, apply a $sim ! 10 , {rm G}$ longitudinal magnetic field, and use polarization modulation/lock-in detection to measure optical rotation amplitudes of order 1 mrad with noise near 1 $mu$rad. We compare the Faraday rotation amplitude of the $E2$ transition to that of the $^3!P_0 -, ^3!P_1$ 1279 nm magnetic dipole ($M1$) transition under identical sample conditions.
rate research
Read More
We present the detection of the highly forbidden $2^{3!}S_1 rightarrow 3^{3!}S_1$ atomic transition in helium, the weakest transition observed in any neutral atom. Our measurements of the transition frequency, upper state lifetime, and transition strength agree well with published theoretical values, and can lead to tests of both QED contributions and different QED frameworks. To measure such a weak transition, we developed two methods using ultracold metastable ($2^{3!}S_1$) helium atoms: low background direct detection of excited then decayed atoms for sensitive measurement of the transition frequency and lifetime; and a pulsed atom laser heating measurement for determining the transition strength. These methods could possibly be applied to other atoms, providing new tools in the search for ultra-weak transitions and precision metrology.
The workhorse of atomic physics, quantum electrodynamics, is one of the best-tested theories in physics. However recent discrepancies have shed doubt on its accuracy for complex atomic systems. To facilitate the development of the theory further we aim to measure transition dipole matrix elements of metastable helium (He*) (the ideal 3 body test-bed) to the highest accuracy thus far. We have undertaken a measurement of the `tune-out wavelength which occurs when the contributions to the dynamic polarizability from all atomic transitions sum to zero; thus illuminating an atom with this wavelength of light then produces no net energy shift. This provides a strict constraint on the transition dipole matrix elements without the complication and inaccuracy of other methods. Using a novel atom-laser based technique we have made the first measurement of the tune-out wavelength in metastable helium between the $3^{3}P_{1,2,3}$ and $2^{3}P_{1,2,3}$ states at 413.07(2) nm which compares well with the predicted valuecite{Mitroy2013} of 413.02(9) nm. We have additionally developed many of the methods necessary to improve this measurement to the 100 fm level of accuracy where it will form the most accurate determination of transition rate information ever made in He* and provide a stringent test for atomic QED simulations. We believe this measurement to be one of the most sensitive ever made of an optical dipole potential, able to detect changes in potentials of $sim$200 pK and is widely applicable to other species and areas of atom optics.
Despite quantum electrodynamics (QED) being one of the most stringently tested theories underpinning modern physics, recent precision atomic spectroscopy measurements have uncovered several small discrepancies between experiment and theory. One particularly powerful experimental observable that tests QED independently of traditional energy level measurements is the `tune-out frequency, where the dynamic polarizability vanishes and the atom does not interact with applied laser light. In this work, we measure the `tune-out frequency for the $2^{3!}S_1$ state of helium between transitions to the $2^{3!}P$ and $3^{3!}P$ manifolds and compare it to new theoretical QED calculations. The experimentally determined value of $725,736,700,$$(40_{mathrm{stat}},260_{mathrm{syst}})$ MHz is within ${sim} 2.5sigma$ of theory ($725,736,053(9)$ MHz), and importantly resolves both the QED contributions (${sim} 30 sigma$) and novel retardation (${sim} 2 sigma$) corrections.
Electromagnetic observables are able to give insight into collective and emergent features in nuclei, including nuclear clustering. These observables also provide strong constraints for ab initio theory, but comparison of these observables between theory and experiment can be difficult due to the lack of convergence for relevant calculated values, such as $E2$ transition strengths. By comparing the ratios of $E2$ transition strengths for mirror transitions, we find that a wide range of ab initio calculations give robust and consistent predictions for this ratio. To experimentally test the validity of these ab initio predictions, we performed a Coulomb excitation experiment to measure the $B(E2; 3/2^- rightarrow 1/2^-)$ transition strength in $^7$Be for the first time. A $B(E2; 3/2^- rightarrow 1/2^-)$ value of $26(6)(3) , e^2 mathrm{fm}^4$ was deduced from the measured Coulomb excitation cross section. This result is used with the experimentally known $^7$Li $B(E2; 3/2^- rightarrow 1/2^-)$ value to provide an experimental ratio to compare with the ab initio predictions. Our experimental value is consistent with the theoretical ratios within $1 sigma$ uncertainty, giving experimental support for the value of these ratios. Further work in both theory and experiment can give insight into the robustness of these ratios and their physical meaning.
We report measurements of the electric dipole matrix elements of the $^{133}$Cs $ $ $6s,^2S_{1/2} rightarrow 7p,^2P_{1/2}$ and $6s,^2S_{1/2} rightarrow 7p,^2P_{3/2}$ transitions. Each of these determinations is based on direct, precise comparisons of the absorption coefficients between two absorption lines. For the $langle 6s,^2S_{1/2}||r|| 7p,^2P_{3/2} rangle$ matrix element, we measure the ratio of the absorption coefficient on this line with that of the D$_1$ transition, $6s,^2S_{1/2} rightarrow 6p,^2P_{1/2}$. The matrix element of the D$_1$ line has been determined with high precision previously by many groups. For the $langle 6s,^2S_{1/2}||r|| 7p,^2P_{1/2} rangle$ matrix element, we measure the ratio of the absorption coefficient on this line with that of the $6s,^2S_{1/2} rightarrow 7p,^2P_{3/2}$ transition. Our results for these matrix elements are $langle 6s,^2S_{1/2}||r|| 7p,^2P_{3/2} rangle = 0.57417 : (57)~a_0$ and $langle 6s,^2S_{1/2}||r|| 7p,^2P_{1/2} rangle = 0.27810 : (45)~a_0$. These measurements have implications for the interpretation of parity nonconservation in atoms.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
