Metastable atoms optical pumping

Gas-discharge lamps are used to optically pump the metastable helium atoms into a higher excited electronic state, which has a dipole-allowed transition to the ground state. Only He (2 S) can be pumped selectively, thereby producing pure He(23S) beams. For the heavier rare gases, both metastable states are equally pumped by gas-discharge lamps. The use of cutoff filters to selectively pump one state is not adequate because of the temperature dependence of the filter transmission and the low / numbers of the pumping transition. Metastable neon can be selectively pumped by a continuous wave (cw) dye laser,60 whereas Ar, Kr, and Xe have so far only been selectively pumped by pulsed dye lasers.61... 

Spin-orbit state selection by optical pumping is exemplified in Fig. 1 by the barium atom. The distribution in the spin-orbit levels of the metastable 6s5d term can be altered by irradiation on 5 of the lines of the 5d6p po <- 6s5d multiplet near 600 nm. If a cw laser is tuned to one of these atomic lines, then absorption and stimulated emission will occur at a rate proportional to the laser power. The upper level can also decay spontaneously to other lower spin-orbit levels, hence transferring jx)pulation permanently out of the initially pumped state. 

In our laboratory, a series of studies of spin-orbit effects in reactions of alkaline earth atoms has been carried out [36-42]. Optical pumping state selection has been employed in order to determine the relative reactivity of the individual spin-orbit levels of metastable Ca( P ), Sr( pO), and Ba( D) atoms. For most of the reactions studied, the products can be formed in the ground electronic state,... 

The alkaline earth atoms studied all have a second metastable level ( D) whose internal energy is slightly higher than that of the metastable triplet level [12], For most of the reactions investigated, the reaction yields significant chemiluminescence, (hi fact, for some reactions, e,g, M + CH3Q, all of the observed chemiluminescence arises fiom this source [38]), For Ca and Ba, it was possible to correct for the presence of this reaction by optical pumping depletion of the Id level [38,41]. 

Measurement of atomic densities by optical absorption A knowledge of the densities of atoms in the ground and metastable levels is often essential for the interpretation of data in atomic collision experiments. This is particularly true for the alkali metals where optical pumping experiments are frequently used to determine collision cross-sections. Since data obtained from vapour pressure tables are unreliable, the required densities are often obtained by measuring the absorption of the gas or vapour when illuminated by light of the resonance or other suitable lines. 

Principles of the magnetic resonance technique. By means of optical pumping techniques large population differences can be generated between the Zeeman levels JMj> or IFMp> of the ground or metastable states of a sample of free atoms. If these atoms are then subjected-to a radio... 

Two kinds of ion species are involved depending on their atomic level properties. One has two optical/peripheral electrons, such as A1+, In+, where the clock transition is based on a dipolar electric transition, and the other has only one optical electron, such as Ca+, Hg +, Sr+, and Yb+, for which the clock transition is based on either a quadrupolar or an octopolar dipole electric transition. With the first kind of ion, the cooling transition is cycling wherein 100% of the atoms relax to the lower level, while the cooling transition (nS to nP) of the second kind relaxes to two different-orbital lower levels the fundamental ( 5) and one metastable level ((n-1) D). The value of the relaxation branching ratio between the nS and metastable (n-1) D levels is such that a significant fraction of ions will populate the metastable (n-l)D level. Thus, another laser is required to pump the atomic ions from the (n-l)D level back to the optically excited state nP. 

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