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Bi when the extra fi meld B saianieg stronger as compared ed with the ipternal fields, the, : je coupling between ali and B’ exces that pals ae and s and the precession, PP about B B becomes faster than that of [ and 3 about, “F. Under these conditions the ome between L” and §”, js partially broken —. and 5 is no foueer § fixed =, , magnitude, As the field B” is further i acres, ic and 5”, ‘slart precessing independently about B with quantised, components Lz and Sz along the field direction (Z-axis),, geen in Fig. 8. . magnitudes of these components are, , Mi » anti Ms respectively, where the magnetic, , quantum numbers M, and Ms take the following discrete, values :, , : ML, 1,0.~—2, and ie 8. 8S — 1, S -— 2, vveacccs. ie, By Larmor’s theorem, the angular velocities of precession of, , , , (Fig. 8), , Land S’ about the field B’ are given by the product of B, and the corresponding ratios of the magnetic moments with the angular momenta. That is,, , om = 5B, , and Qs = oie, The energy of each precession is equal to the product of the angular velocity and the, , Projection of the corresponding angular momentum vector aloge the field direction. That, is,, BM, i, AE, = lz = Fm ue, AEs = @sSz = 25 BMs, , of these two interaction energies is the main energy shift AE from the, ed energy level. Thus ;, , , , , , AE = AE, + AEs, , eh, =(M, + 2s) a, , , , , , , , , , = eo ae eB ., = (M, +2 MS) ayme pace

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‘1. Observed Stark Effect in Hydrogen, In 1913, J. Stark discovered that the Balmer lines emitted by hydrogen atoms place, , in an electric field of the order of 10° V/cm are split into a number of pol, components, When viewed perpendicular to the field, some of the components of each jj, are plane-polarised with the electric vector parallel to the field (1 components), an, others are polarised with electric vector perpendicular to the field (o components),, viewed parallel to the field, only the o components appear which are now unpol, , §, This splitting of spectral lines in an electric field is known as ‘Stark effect’. It play:, important part in the theories of molecule formati, lines, and dielectric constants., , Hg shows a larger number of St, components than H,, the line Hy showing still more larger number., (ii) The wave-number shifts are inte, trength of the electric field, and is same for all hydrogen lines,, , Except = the absence of circular polarisation in longitudinal observati, Porperties of Stark lines Tesemble those of the Zeeman lines. But, in, , ater shifts than the O-components.. —, wer energy states (small n), such as, , nal to the field Strength about their J, or the ‘linear’ Stark effect., , , , , , , , gral multiples of a unit which is proporti, , symmetrical splitting Proportio:, his is known as the “first, : order’, lines mvolving the higher state