Chakravarty, A S

Chatterjee, R

English

IACS Institutional Repository

ON THE OPTICAL ABSORPTION SPECTRA OF Ni*+.6HgO COMPLEX IN CRYSTALSA. S. OHAKRAVARTY a n d  R. CRATTERJEEDepartment ok Maonetism,!I n d ia n  A ssoiuation  for  the ('Jitltivation pF Sc ie n c e ,Jadavpur, Calcutta-32. j {Receivv(J Auqufit 7. UUil),'In crystalline electriit field of symmetry (),,, tli4 gronndstate of the Ni*' ion is split into three components Ki.,. F^,2, f^itli Successively increasingenergy. In considering the absorption spectra, thd transitions to the upper level as also the forbidden transition to th(‘ singlets X^), and bSf with low transi­tion probabilities should b(^  taken into account; All these transitions have energies of the order of 10^  enr^ and since they take place only in combination with suitable vibrational transitions, the intensities of the light absorptions must be lower than if they had been due to pure electronic transitions. The three main transitions (*P) give rise tob road bandscalled hereafter T, IT and III over which the other weaker lines are superim- poseil.For the aijiieous solutions of several hydrated salts of Ni^ ^^  Dreisch ei al, (1937, 1939) found that the peak of band f lies at 8300 enr h peak of iiand II at 14100 cin“  ^ and peak of band ITT at 25000 cm h This has been confirmed by Hartmann and Muller’s (1958) observation of the absorption spectra o f NiS04, fiH^O and NiS04, 7Hj,0 crystals. Hartmann and MuIUm* (1958; cf. Mookherjee et ah 1960) have been able to resolve the bands II and III into several peaks, e.g,, band II into three peaks C, £), E of more or less the same intensity and a of much smaller intensity; band III into two peaks F, G of nearly the same intensity as the peaks of II, and three other ft, c and d of much smaller intensity. They obtained further two more very weak peaks e j  near 39000 cm h They could apparently explain all these peaks except E, on the basis of the splitting of the different states of the Ni''^  ^ ion caused by a small tetragonal field superimposed upon cubic field (Fig. LbSince the intensity of this band E is almost equal to the transitions from other Stark levels, it cannot be due to any intercombination between terms of different multiplicity (Orgel 1965). Contention of Ballhausen (1955) and Hartmann and Muller (1958) that the occurrence of this band is due to (L.S.) coupling effect has been also contradicted by Jorgensen (1958). On the other hand. Mookherjee10643644 Letters to the Editoret al (I960) hav<‘ shown tliat the observed anisotropy of Ni‘'“  ion : Kj. — ATjj =  ;5i>4- X IO-“, assuming a tetragonal field, does not agree with the splitting C-*D  ss 300E n orp 3^  Jovol cliagram  o f  N i( cubn*and o rth orh om b ic  fit>ld,(N o t draw n to  scale)l)ut with the splitting 1300 cm Tn that case the peak 1)remains unexplained. Paramagnetic resonance studies of several salts of by Griffiths and Owen (1952) show that the electric held in all these salts has really an orthorhombic symmetry, We have therefore assumed an orthorhombic field in all these salts and been able to prove that all the three peaks (\ D and E are really due to transitions from ground 3-4 2 level to the three components o f the level split up by the orthorhombic field.We have neglected the effect of the spin-orbit interaction, which being asecond order effect, is not so important in the case of optical absorption of Ni*+,Letters to the Editor 6456H2O complex and the inclusion of this in the Hamiltonian would unnecessarily complicate the present calculations, meant to explain the existing experimental fa(?ts, as far as they go.Following the method of Van Vletik (1932), and Sehlapp and Penney (1932), Tanabe and Sugano (1954), Pryce and Runciman (1958) and taking into consi­deration all the energy states as already mentioned, wf have calculated the energy levels of GHgO with the following cubic and orfljiorhoinbic field parameters(Table 1). and compared them with the experimental values obtained by the afoiementioned authors. All things ccmsidered the pt is much better than that obtained by Hartmann and Muller. Authors have i,lso worked out a complete theory o f the susceptibility of ion in an orthorhombic field wdiich will bediscussed in a future communication.The authors an* grateful to Prof. A Rose, D.So., F.N.I., for suggesting the problem and helpful criticism of the work.TABLF 1(hibic field parameter I>,j - SIO cm ^Orthorhombic field ])arameters (t - —70 cmRacah j>arameters F* 1030 mu  ^ F ~ 4850 cm~^S =- 20 cm~*S]>litt iijgH ( 'Hleulal'Od valiios X 10-3 om-J.ExpcMinif^ ntal values X *.7.957 (A) S.OlO (O') 1 8.097 (li)8.30014.130 (C)14.405 (D )ir  15.423 (E)13.90014.20015.20017.230 (a) 17.500—>3’F2« (*1-)*(t) 24.81J (b) 23.900(«P) 25.030 (V) 25.08(* (Cr) 111 25.120 (0)25.400—>lAi</ (»l)U.O 20.941 (c) 26.900— (iDKl) 30. HU) (cl) 30.050(in id)(iDi(J)35.879 fo) 30.399 (f) 39.000(18) 67.929 (g)646 Letkrs to the EditorR ’ E F E R E N 0 K 8Bftllhaunen, C. J.. 1955, ('. J. Ugl D tm h  Vivdmkab., SeUkah, M<a,fgs. MeM. No. 8 29.UmiHch., Th. ami Kallschcm'r, ()., 1939, Z . Phys. O h m ., B45, 19.Urifflths, J .  H. and Owen, J . .  1952, Pror. Soy. Soc., A. 213, 4-5I.Hartmann, H. and Mullor, U.. 1958, D m . Farad. Soc. 26. 49.Jorganson, C. K., 1958, D m . Farad. Soc., 26, 90.Mookhorji, A. and Chhonkar, N. 8., 1960, 7«d. J .  PhyH., 48. 363.Orgol, K„ 1955, ./. ('hm. Phy^., 28, 1004.I’ ryce, M. H. L, and Runeimann, W. A.. 1958, D m . Farad. Soc., 26, 34. ^Srhalpj), R. and IVunny, W. G ., 1932, Phyn. S n \ , 42, 066.Tanabe, Y. and Sugano, 8., 1954. Proc. Pliyn. Soc. Japan, 9. 753, 766.Van Vleck. J. H.. 1932, Phys. Sci\. 41, 2(»«.

On the Optical Absorption Spectra of  Ni2+6H2O Complex in Crystals

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On the Optical Absorption Spectra of Ni2+6H2O Complex in Crystals

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