Rao, P Tiruvenganna

Rao, S V Krishna

English

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THE SPECTRUM OF CoCl IN THE PHOTOGRAPHIC INFRARED AND THE VISIBLES. V. KRISHNA RAO and P. TIRUVENGANNA RAOP hysics Department, Andhra University, W altair .{Received July  13, 1961)Plate XII A & BABSTRACT. The spectrum of CoCl has been examined in the photographic infrared and the visible using both low and high dispersion. Several new brief systoiiiR have been observed in the visible region X 4600— X5100 A, and in the iihotographie infrared region X 6850— X 7950 A. Vibrational constants of the various systiuns have been d(*rived from the analyses. The new systems, designated in this paper as F, O, H, 1 are observed to consist of single headed bands while the remaining systems 5, K, L, Nj, and O are observed to bo double headed. It is suggested that tho two systems Ni and Nu in the iihotograiihic in­frared might belong to two components of a an— transition. ,I N T R O D U C T I O NThe band spectrum of cobalt chloride has been investigated by several earlier workers, Mesnage (1935), More (1938). and Krishnamurty (1952). On the basis of high dispersion spectrograms, taken in the second order of a 21 ft. concace grating spectrograph, More (1938) gave vibrational analyses of three systems designated by him as 1, 2 and 3 in the region (A4200—A475()l). The bands in each of the three systems are single-headed and degraded to longer wavelengths. Recently, Krishnamurty has identified two more systems, designated as 4 and 5 in the same spectral region. These consist also of bands degraded to longer wavelengths. In addition, Krishnamurty proposed the vibrational analyses of six groups of line-like bands slightly degraded to red in the region (AfiSfiO—AfiOOOA). on the basis of a ®II— transition. His analysis was however based on measure­ments of plates taken under low dispersion, (25—30A/mm).In a previous paper (Rao et al, 1961) we have reported the results of a study of the spectrum of NiOl in the photographic infraa-ed under high dispersion. In continuation of this work we have examined the spectrum of CoCl in the photo­graphic infrared and the visible, both under low and high dispersion. This work has disclosed the existence of a number of new band systems of CoCl in the photo­graphic infrared region (A6850—A7950 A), and in the visible region (A4600 A5100 A) The structure and analyses of these new band systems are discussed in this paper.E X P E R I M E N T A LThe spectra were excited both in a heavy current discharge from a 2000 volt d.c. generator and in a high frequency discharge from a 100 watt oscillator61656using an anhydrous B.D.H. sample of CoCla- The spectra were photographed under low dispersion on a Hilger three prism glass Littrow instrument (17 A/mm), and also in the first and seccjnd orders of a 21 ft. concave grating spectrograph (dispersion 2.5 A/mm and 1.25A/mm) using appropriate filters. Exposui'es of two to five hours duration were found necessary for obtaining the spectra on the grating, using Kodak l.N. plates and Agfa Isopan plates. Second order iron arc lines were used as standards for measurements of all grating plates.The Spectrum of GoCl in the Photographic^ etc. 557K K H U L T S  A N D  A N A  1 - ^  S T SAll the five band^systeius observed and analysed by More (1938) and Krishna- murty, (19e52) in the spectral region (A4200—A4750A) were photographed in the present work lioth under low and high dispeijfiion. In tlie order of increasing wavelength, systems 3, 2, 4, 5 and 1 are designated as.A, B, 0,1), E respectively. The bands in each of the systems appear single headed and arise from a transition in wdiich A A 0 in Hund’s case ‘a' or Ad =- 0 in Hiind’s case ‘c\The six groups of line like bands (designated as M  in this paper) observed and analysed by Krishnaiuurty in the region (A5350—A(iOOoA) were too weak to be photographed under high dispersion and therefore they are not considered in the present work. In the spectrum of CoCl excited in a high frequency dis­charge from a 100 Watt oscillator we have observed a number of now band systems in the region (A4600-A5100A). According to our analyses, based on a close s(rrutiny of both low and high dispersion spectrograms, the bands of OoCl in this region were classified as belonging to seven separate brief systems. Each of these systems is characterised by a strong Ar -  0 sequence with weaker A« = - l  or - f  1 sequence. In the order of increasing wavelength these were designated as F, O, II, I  J, K  and L  systems respectively. The bands in each of the systems F, and I  arc single headed, degraded to red and interpreted as the R  heads.The bands in J, K  and L systems arc double headed and interpreted as the R  and Q heads. The data and classifications of these bands are given in Table I Low dispersion spectrograms of these seven systems are shown in strips (a and b) in Plate X II A, Fig. 1. Grating spectrograms of the prominent bands of the strong Av =  0 sequence in tlifferent systems are shown in strips (a, 6andc)m  Plate X II B, Fig. 2. In the bands of the weaker Av =  ± 1  sequences only the heads of the’ more abundant Co*®Cl species could be identified.In the spectrum of CoCl excited in a heavy current discharge from a 2 ( ^  volt D C. generator we have observed two new systems of bands in the photo- graphic infrared region (A6850-A7960A). The observed spectrum m the region (A6850-A7200A) taken under low dispersion can be seen from n f tb JLPlate X II A Fig. I, to consist of four characteristic groups of bands. Of t h ^ ,  ^ o  sS n ger grLps beginning at A =  7117.oA and A7171.2A are identified as th . two A* -  0 o f two compon.nt. of .  -n  - ' S  t™ .lOon. Thegroup, begtaping at A -  6892-8A «rd  A -  6941.2 « e  .d.nt.ae<l «  two if . -558 S. V. Krishna Rao and P. Tiruvenganna Bao±1 sequences respectively. The double headed nature of the bands of this system designated as N(Ni and N )^ can be seen clearly from grating spectrograms shown in strip (d) in Plate XII B, Fig. 2. The data and classification of the bands are given in Table II.TABLE IBand heads of CoCl in the region (A4600—A5100A)Wavoiiurnix'r Int. Clas«ifioat?on Wavenumber Int. ClassificationHvaiein—F 2lfi40.4 8 0,0system—.T 20358.4 7 1,0 R21630.0 8 l.l 20356.4 5 1,0 Q21230. r> 5 0.1 20330.4 6 2,1 R2122)<.2 5 U? 20.337.7 6 2.1 Q21225.2 5 2,3 19050.9 0 0,0 Rcystf^ ni—G 10945.8 0 0,0 Q21335.1 8 0,0 10027.5 8 1,1 R21320.0 8 U 19925.1 8 1,1 Q21306.0 8 2,2 systoni—‘K20033.1* 5 0.1 20279,0 5 1,0 R20023.4* 5 1.2 20277.5 4 1,0 Q20014.2* 5 2.3 20263.1 5 2,1 Rsystem—H 20260.3 5 2,1 Q21263.0 10 0,0 \0S60.7 10 0.0 R212^1 1 ■rI 1,1 10868.1 10 0,0 Q21247.2 6 2,2 10851,9 8 1,1 R20847.0* 3 \^1 10840.9 8 1,1 Q20842.0* 4 1.2 system—L20832.7* 4 2,3 19829.5 9 0,0 R20825 8* 4 3,4 19826.3 0 0,0 Qsy.*3tem—I 10804.3 0 1,1 R21372 5* 3 1,0 10801.2 9 U  Q21365.2* 3 2,1 19781.2 7 2,2 R21357.0* 3 3.2 19779.2 7 2,2 Q20960.1* 7 0,0 ♦Measured on low dispersion plates only.20963.4* 5 1,1K lISHNA RAO AND P. T. RAOIndian Journal of Physics. Vol. X X X V , No. 11PLATE XII A4512C 4 .6 9 1 -4 4.789-6OpF111AVrO |a v ? - iAV:0 1 AVc-lAX A V r O4878-2 50(2.0 5 /52-3GHIFig. I • New band systems o f C o C l in the photographic infrared and the visible ( low dispersion spectrograms). a — systems F , G ,  H and 1. b — systems J , K  and L. c — systems N  i , N i  and 0 .KRISHNA RAO AND P. T. RAO4 6 fl • 2Indian Journal o f  Physics, Vol. X XX V, No nPLATE XI B4 .6 5 4  S0,0 i,i 2,2 ® ooi;2 ;l ^soo'hz S O S / 6N, otoTM . ■' 0.0 «.» 2,25  oi l  i!ii - ’I  N ,U op u 2.23935*8Fig. 2. New band systems o f C o C l in the photographic infrared and the visible (21 ft. grating spectrograms), a — sequence o f system F. b — .=() sequence o f systems G , H .c — A V --0  sequence o f systems J ,  K  and L . d — A V - 0  sequence o f systems N i and N 2. e — aV=0 sequence o f  system O.In the region (A7600 ~-A7950A) a weaker system (designated as 0) shown in strips (c) in Plate X II A, Fig. 1 and (e) in Plate X II B, Fig. 2, has been observed. The strong group beginning at A ~  7882’4A is identified as the Ar =  0 sequence and the weaker group beginning at A ~  7612.2 A as A?’ —+  1 sequence. In the Av =  0 sequence tlie R and Q heads are identified while in the weaker Av =  +  1 sequence only R heads have been identified. The data and classifications of the bands are given in Tabl^ II. Table III summarizes the vibrational constants of the different band systems of CoVA,The Spectrum of CoCl in the Photographic^ etc 559TABLE IT :Band heads of CoCl in the regioni (A6850—A7950A)W a v on u ra b or In t . C lassification W a v c im m b o r ' In t . CMassiOcationsy s te m — N i Hj'StOlll—k-O1 4 6 0 3 .0 4 1,0 Jl 13169 .1 4 \,i) R1 4 5 0 1 .4 4 1,0 Q 13130.8 6 2,1 R1 4 4 8 3 .3 4 2,1 K 13098 .8 5 3,2 U1 4 4 8 0 .4 5 2,1 Q 12683 .0 7 0,0 R1 4 4 6 1 .6 6 3,2 H J2674 6 6 0 ,0  Q1 4 4 6 0 .0 6 3,2 Q 1 2658 .6 S I ,l  R1 4 0 4 7 .0 3 0,0 n 12650.6 7 1.1 Q1 4 0 4 4 .2 3 0,0 Q 12628 .2 s 2,2 R1 4 0 31 .2 5 1,111 1 2 621 .8 8 2,2 Q1 4 026 .1 5 1,1 Q --------------------------- - ----- - ■ ---------1 4 0 1 2 .4 * L 2,2 Q *iSiipc?’|>osc(l by  a tom ic  lim*.sy s te m — 5^ 21 4 4 0 2 .8 4 1,0 Q1 4 3 8 0 .4 6 2,1 Q14.380.7 6 3,2 Q1 3 9 4 0 .8 4 0,0  R1 3 9 3 7 .7 4 0,0 Q1 3 924 .1 6 1,1 R1 3 9 2 0 .3 7 1,1 Q1 3 9 0 4 .0 6 2,2 R1 3 8 0 9 .7 10 2,2 Q560SystnFnABCDEFQHTJKLMNiNo()/S'. F. Krishna Rao and P. Tiruvenganna RaoTABLE IIISummary of the vibrational constants of CoClW»iv(? miinbor oft ho (0,0) ban'l wo' xo'wo' wo"22066.222402.7 2 2 1 8 2 . r>22072.322014.821640.421335.121263.920969.1 19945.819868.1 19826.3 J74S4.114044.2 13937.7 12683.0420.0416.6401.0410.2420.0408.0391.2413.2405.0408.6408.4412.3462.5 467 6 478.81 66 0.821.142.152.000.80-1.00-0 .502.651.251.38421.8419.4416.2416.4421.2409.0407.1416.8409.0 431 .0428.0416.0 482.6484.3498.4xo wo1.340.280.74— 0.452 .5 50.383.65 0.90 -1 .05D I S C U S S I O NFrom the magnitude of the vibrational constants o f the upper and lower states, More (11)38) has suggested that systems A, B and E might belong to a triplet-triplet transition, with intervals of 390 and 562 After the ientificationof two more systems C and D, Krishnamurty considers that systems E, T> and C with separations of 55 and 110 cm"“^  may better be represented as belonging to an electronic triplet, while A and B may be identified as two component systems of a triplet-^ triplet transition. A(*.cording to us, each of the brief systems A to I consisting of single headed bands arises from a transition with A A — 0 in Hund’s case (a). However in view of the large multiplct splittings known in the ground and low excited states of Coj, it is possible that they are all separate systems with Aq — 0 corresponding to Hund's case (c). This view is supported by the fact that Heimer, (1937) from a detailed rotational analysis o f CoH bands, has previously identified the A -^X  transition in CoH as o  =  4-> (1 =  4 with Aq =  0, corres­ponding to Hund’s case (c).The characteristic appearance of the and N2 systems observed in the phf>to- graphic infrared region (A0H5O—A72()()A) sliown in strip (d) in Plate XII B, Fig. 2, would suggest that they may arise from two components of a ^1'— transition. The magnitude of the vibrational constants of the upper and lower states, the observed double headed nature of the bands, and the close proximity of these two systems lend support to this view. Howevei*, both the upper and lower states of this 1^1— transition do not correspond to those obsei’ved already in the visible region. They appear to belong to two different excited states of the CoCl molecule. A similar situation is also ol^served in the band systems of MnF, MnCl and MnBr in the ])hotograi)hic infrared.A ( X 0 W L E D a  M SE N TThe authors are indebted to Prof. K. R. Rap for his interest in the progress o f this work. One of the authors (S.V.K.) acl^owledges the financial support from the Council of S(*ientifi(^  and Industrial Research.The Spectrum  o f G o d  in the PhotognphiCj elCj 561K E F E R R X c: K RHcimcr, A , 11)37, Z. 105, r>0.Krislinamiirty, V. H., h n l. J. P h y s ., 26. 177.K rislnm irnirtV , V . O ., 10r>2. T hoMiw fo r  P o(*lornt(', A n dh ra  TTniv.,’W alta ir. McsnaRc, P. 11)35, /?., A c a d . Sc^, P a r is . , 200, 2072.Mcsnngo, P., 1030, Ann. d. Phys.. 12, 5.More, K. R., 1038, Phyf^. P r v . 54, 122.K a o ., 1001, Z . Phynh. (in jm’chs)

The Spectrum of CoCl in the Photographic Infrared and the Visible

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The Spectrum of CoCl in the Photographic Infrared and the Visible

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