Frequency evaluation of the doubly forbidden $^1S_0\to ^3P_0$ transition in bosonic $^{174}$Yb

Exploration of the magnetic-field-induced $5s5p$~$^3P_0$~-~$5s^2$~$^1S_0$ forbidden transition in bosonic Sr atom

We presented experimental and theoretical studies of the effect of an external magnetic field on the forbidden transition in the bosonic Sr atom. In our ultra-cold atomic system, the excitation fraction of $5s5p$~$^3P_0$~-~$5s^2$~$^1S_0$ forbidden transition was measured under the circumstance of the different magnetic field strengths by using the normalized detection method. Based on perturbation theory, we calculated the magnetic-field-induced $5s5p$~$^3P_0$~-~$5s^2$~$^1S_0$ transition rate. The excitation fraction as a function of the magnetic field strength was deduced according to the cal…

Collision strengths and transition probabilities for Co III forbidden lines

In this paper we compute the collision strengths and their thermally-averaged Maxwellian values for electron transitions between the fifteen lowest levels of doubly-ionised cobalt, Co^{2+}, which give rise to forbidden emission lines in the visible and infrared region of spectrum. The calculations also include transition probabilities and predicted relative line emissivities. The data are particularly useful for analysing the thermodynamic conditions of supernova ejecta.

强禁戒光学钟跃迁的共线三光子激发

Collinear Three-Photon Excitation of a Strongly Forbidden Optical Clock Transition

本文针对玻色子锶同位素中强禁戒的${{^1\rm{S}_0}\text{-}{^3\rm{P}_0}}$钟跃迁，提出弱磁场下共线三光子激发方法，实现相干激发并观测到高频率拉比振荡，为降低原子钟系统误差及下一代量子传感器应用奠定基础。

Effective collision strengths for excitation and de-excitation of nebular [O III] optical and infrared lines with kappa distributed electron energies

We present effective collision strengths for electron excitation and de-excitation of the ten forbidden transitions between the five lowest energy levels of the astronomically abundant doubly-ionised oxygen ion, O^{2+}. The raw collision strength data were obtained from an R-matrix intermediate coupling calculation using the Breit-Pauli relativistic approximation published previously by the authors. The effective collision strengths were calculated with kappa-distributed electron energies and are tabulated as a function of the electron temperature and kappa.

Accurate spectroscopy of Sr atoms

We report the frequency measurement with an accuracy in the 100 kHz range of several optical transitions of atomic Sr : $^1S_0- ^3P_1$ at 689 nm, $^3P_1- ^3S_1$ at 688 nm and $^3P_0- ^3S_1$ at 679 nm. Measurements are performed with a frequency chain based on a femtosecond laser referenced to primary frequency standards. They allowed the indirect determination with a 70 kHz uncertainty of the frequency of the doubly forbidden $5s^2^1S_0- 5s5p^3P_0$ transition of $^{87}$Sr at 698 nm and in a second step its direct observation. Frequency measurements are performed for $^{88}$Sr and $^{87}$Sr, al…

Optical lattice clocks with weakly bound molecules

Optical molecular clocks promise unparalleled sensitivity to the temporal variation of the electron-to-proton mass ratio and insight into possible new physics beyond the Standard Model. We propose to realize a molecular clock with bosonic $^{174}$Yb$_2$ molecules, where the forbidden $^1$S$_0$$\rightarrow$$^3$P$_0$ clock transition would be induced magnetically. The use of a bosonic species avoids possible complications due to hyperfine structure present in fermionic species. While direct clock line photoassociation would be challenging, weakly bound ground state molecules could be produced by…