Intercombination lines

Thus, the kind and quantity of relativistic corrections to the length and velocity forms of 1-radiation are different. From this point of view the concept of the equivalency of these forms must be improved both forms will lead to coinciding transition values for the accurate (exact) wave functions only if we account for the relativistic corrections of order v2/c2 to the transition operators (in practice, only for the velocity form). The other conclusion accounting for the relativistic effects leads to qualitatively new results, namely, to new operators, which allow not only improved values of permitted transitions, but also describe a number of lines, which earlier were forbidden. These relativistic corrections usually are very small, but they are very important for weak intercombination lines of light neutral atoms (see Chapter 30). 

Approximate selection rules. Intermediate coupling. Intercombination lines... 

Where does this spectacular development lead concerning frequency standards Traps for neutral atoms unfortunately perturb the atomic energy levels both the magnetic fields used as well as the laser light for cooling. As an example of what can be achieved, mention may be made of a tuneable dye laser, locked to the intercombination line at 657 nm of Ca atoms, either in an atomic beam or in a magneto-optic trap, has an estimated relative uncertainty of below 10 [38]. 

Another impressive example is work made at Physikalisch-Technische Bundesanstalt in Braunschweig [38], The optical frequency of the intercombination line, Pi- So, at 657 nm in has been measured, both in an atomic beam as well as with trapping/cooling techniques. This transition was connected all the way to the Cs frequency by a chain giving a total uncertainty of the absolute frequency for their measurements as low as 10 which is the lowest uncertainty in the visible domain. This transition has a linewidth < 400 Hz which gives good prospects of considerably improving the results. 

The increased spectral resolution obtained with the Ramsey technique because of the increased interaction time allows the direct observation of recoil doublets in atomic or molecular transitions (Sect. 9.1.1). An example is the Ramsey spectroscopy of the intercombination line in calcium at k = 657 nm [1268], where a linewidth... 

Fig. 9.62 Ramsey resonances of the calcium intercombination line at X = 657 nm, measured in a collimated Ca atomic beam ...

What is the probability that a photon, emitted from a Ca atom at the centre of a spherical cloud with radius R = 1 cm on the intercombination line Pi 5o at X = 657 nm with the natural line-width An = 3 kHz is reabsorbed by another... 

Fig. 14.43a,b. Ramsey resonances of the calcium intercombination line at A. = 657 nm, measured in a collimated Ca atomic beam (a) Doppler profile with a reduced Doppler width and a central Lamb dip, if only one interaction zone is used (b) expanded section of the Lamb dip with the two recoil components observed with three interaction zones with separations L = 3.5 cm and L = 1.7 cm. The dashed curves show results with partial suppression of one recoil component [14.114]... 

Even at small deviations from LS coupling transitions between states of different multiplicity intercombination lines) are observed. 

Even at small deviations from LS coupling, transitions between states of different multiplicity intercombination lines) are observed. Sudi lines ai e indicated for the Ca atoms in Fig. 2.7. 

Three strong lines of Ru XXXIII and Rh XXXIV have been identified in laser produced plasmas [11]. The intercombination line 3s Sq-3s3p P has not been observed but systematic comparisons between experiment and MCDF calculations lead to accurate wavelength predictions [12]. The energy levels of all (n = 3) configurations are calculated by relativistic model potential methods [13] and by the relativistic parametric potential method [14], but... 

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