Precision measurement of the energy of the 4d 9 5s 2 2 D 5/2 metastable level in Ag I

Abstract

Abstract. The energy of the 4d95s22Ds/2 metastable level in Ag I, which is the upper level of the very narrow 5 s 2S1/2-4 d 9 5 s 22D5/2 two-photon transition at 661.2 nm, has been determined from precision measurements of the wavelengths of the 206.1 nm (5s2S1/2-6p2P°/2) and 547.5nm (4d9 5s22Ds/2-6p 2P°/2 ) lines emitted from a hollow-cathode discharge. The measured energy of the 4 d 9 5 s 2 2D5/2 level, 30242.286(7) cm -~, is combined with the known hyperfine splittings and the estimated l°7Ag-l°9Ag isotope shift to obtain accurate absolute frequencies for the hyperfine components of the 661.2 nm transition. These results should help in the detection of the narrow 661.2 nm twophoton transition, which has been proposed as a new optical frequency standard. PACS: 32.30Jc; 35.10.Fk I. ln~oducfionThere is currently much interest in the spectroscopy of the Ag I 5s 2S1/2-4d 9 5s 2 2D5/2 two-photon transition at 661.2nm [1][2][3][4] involving the long-lived (~0.2s [5,6]) 4d95s 2 2D5/2 metastable level, which decays by electric quadrupole radiation at 330.6nm. Because of its extremely small natural linewidth (g0.8 Hz), the 5s2S~/2-4d95s22Ds/2 transition when driven by the 661.2 nm Doppler-free two-photon transition in a beam or atomic fountain of laser-cooled silver atoms is a particuiarly attractive candidate for an optical frequency standard [2,3]. However, in order to be able to detect such a narrow two-photon resonance, it is important first to know the absolute frequency of the very weak Tables [9], and these are found to yield resuits that differ by up to 0.5cm -a, or 15GHz (see Table 3). Attempts in this laboratory to detect the very weak 330.6 nm E2 transition in high resolution scans of the emission from a silver hollow-cathode lamp have to date proven to be unsuccessful. In this paper we report a pre-

Calculations of the relativistic effects in many-electron atoms and space-time variation of fundamental constants

“…There are many other atoms which are being studied as possible frequency standards but which are not included in the table. These include Mg I [17], In II [18], Xe I [19], Ag I [20], etc. Note that the biggest relativistic effect is in Hg II.…”

Optical Frequency Standards Based on Molecules, Atoms and Ions

“…Recently, however, Walther and coworkers have trapped about 10 6 atoms, cooled below the Doppler limit, using 40 mW of UV light [74]. In parallel, various groups have performed spectroscopy to localize the frequency of the clock transition, to < 60 MHz [76][77][78]. With current solidstate laser technology, one should have % 100 mW at 328 nm via twice frequency doubling a Nd:YLF source at 1312 nm.…”

Electron-impact excitation of silver

“…Comparing other possible systems such as Ca, Rb, Sr, Yb, and Cs used as optical frequency standards that are based on optically probed electronic transition, usually a forbidden transition, with narrow bandwidth, there has been some interest in silver using a transition between the 4d 10 5s 2 S1/2 ground state and the metastable 4d 9 5s 2 2 D5/2 level, which is an extremely narrow transition with a small natural linewidth (0.8 Hz). Larkins and Hannaford [4] have determined the energy of the 4d 9 5s 2 2 D5/2 metastable level and the frequency of the transition. Badr et al [5] presented a detailed description of this optical two-photon excitation process and determined the frequency, hyperfine coupling constants, and isotope shift of this transition.…”