Mohler and Moor1 observed in the region between 3000 and 2500 A a suite
of absorption bands emitted from zinc vapour, which they ascribed to zinc
oxide. The spectrum of zinc vapour in the same region was found by Walter
and Barrott

D. S. Pešić

English

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CR 0 AT IC A CHEMIC A ACT A 38 (1966) 313 tCCA-442 543.423:546.47-31 Note 0 Emission Spectrum of Zinc Oxide between 6000 and 5000 A D. s. Pesic The Boris Kidri~ Institute of Nuclear Sciences, Belgrade, Serbia, Yugoslavia Received July 13, 1966 Mohler and Moor1 observed in the region between 3000 and 2500 A a suite •of absorption bands emitted from zinc vapour, which they ascribed to zinc •oxide. The spectrum of zinc vapour in the same region was found by Walter .and Barrott2 • On the basis of the experimental conditions they suggested Zn2, ZnCI and ZnO as emitters of these bands. Since it has not been confirmed that '. ZnO is responsible for some of these bands, the results are not reliable and they are not included in Pearse and Gaydon's table3• Egerton and Rudrakan-•chana4 obtained one red-degraded ZnO band at 3435.3 A in diffusion zihc dimethyl flame with oxygen, and in an arc between pure zinc electrodes in ;air and in a mixture of N2 + 0 2 • The band was visible only when oxygen was present, and authors considered it to belong to ZnO rather than to Zn~ ·or ZnN. Parkinson5 observed a band of the same wave-length in emission ·when zinc oxide was subjected to shock excitation in argon, and he suggested a polyatomic oxide of zinc as the emitter in view of the analogy with poly-atomic oxides of earth alkaline metals. To determine zinc by flame photo-·metry6 -s a continuum with a maximum at 5000 A is used. However, no report ·on the emitter of this continuum has been given so far. The purpose of the present investigation was to identify a group of new ·bands in the greenish-yellow region obtained in zinc arc in an atmosphere ·of oxygen. The experimental procedure and the results of the examination of this spectrum are presented. EXPERIMENTAL The emission bands were excited in a vacuum arc using water-cooled spectrograp-hic pure zinc electrodes in an atmosphere of ordinary oxygen and in 98.4°/o oxygen 13. 'The arc was maintained with a 220 volt D. C. and a current of 0.8 Amps. The pressure of 15 mm. Hg was found to be favourable for the arc running. The discharge is of medium intensity and of a blue color. The spectrum was obtained using Hilger .medium and large Littrow quartz prism instruments with a dispersion at 5600 A ·of 88 A/mm. and 30 A/mm. respectively. The investigated region was photographed ·on Ilford HP 3 and Astra III plates. Exposures of 15 minutes on the medium and 1 hour on the large spectrograph were sufficient. The bands were measured against iron arc standard lines. RESULTS The bands started at 5200 A and extended up to nearly 6000 A. The 'Strongest part of the spectrum lay between 5570 and 5800 A. The appearance * Part of the paper was presented at the 2nd Yugoslav Conference for Pure and Applied Chemistry, Belgrade, June 1966. 314 D. S. PE!jJC of the spectrum obtained with ordinary oxygen under low and medium dis-persion is shown in Fig. 1. The mean of several measurements of the main. heads with average precision of 0.2 A, are given in Table 1. A great number of bands are degraded to the red, but some of bands on the short-wave side, either barely degraded to the red or show only a broad maximum. Bands appear diffuse with small dispersion, while under large dispersion they show a line-like structure, and it is difficult to localize the position of the heads .. TABLE I Wavelengths of Outstanding Bands of Zinc in Oxygen 16 'J..,A v, cm.-1 I I* I Deg. II /...,A v, cm.-1 I I Deg .. 5774.0 17314 4 R 5437.3 18386 7 R 5678.9 17604 , 10 R 5369.4 18619 8 R 5619.3 17791 4 R 5326.9 18768 8 R 5581.2 17912 7 R 5312.3 18819 3 R 5523.5 18099 4 R 5264.7 18989 3 M 5461.6 18305 4 R 5224.6 19135 3 M • Intensities in the table are estimated visually on a scale of ten. With the vacuum arc in oxygen 18, the spectrum in the same region was-obtained (Fig. 1. a, b). Table 2 shows measured wavelengths of outstandinK bands. The general appearance of the spectrum is similar to that obtained in ordinary oxygen, but with definite isotope shift. A correlation between bands· obtained in ordinary and isotopic oxygen can be made with certainty only for intense bands. The strongest bands in ordinary oxygen are at 17604,. 'J..,A 5703.3 5640.2 5604.4 5578.7 5546.3 5512 TABLE II Wavelengths of Outstanding Bands of Zinc in Oxygen 18 v,cm.-1 17529 17725 17838 17920 18025 18137 10 4 7 3 3 3 R R R M M M 5370 5258 5225 5006 4958 4892.2 18616 19013 19133 19970 20163 20435 4 4 3 1 2 5 M M M M R R L ,lJ 17791 and 17912 cm.-1 The corresponding bands in oxygen 18 are shifted to' the red and lie at 17529, 17725 and 17838 cm.-1 This is a shift of 75.66 and 74 cm.-1 For weaker bands shifts are also observed, but they are irregular and attempts to establish the correlation between the two systems have had little success. The spectrum described can be with considerable certainty assigned to· a molecule containing only oxygen and zinc atoms. Experiments have shown that oxygen and zinc had to be present for the bands to appear. Measured· well-marked isotope shifts when ordinary oxygen was replaced with oxygen 18, show that oxygen is present in the emitting species. When running zinc arc in an atmosphere of argon, nitrogen, hydrogen and water, no spectra which a b c d Zn 4871.3 5232.9 5763.0 4654.5 5302.3 I 6191.5 I Zn Na Fig. 1. Part of the spectrum showing diffuse zinc oxide bands. Spectra a and d -Zinc metal in vacuum arc in oxygen 18. Spetra b and c -Zinc metal in vacuum arc in oxygen 16. Strips a and b show spectra taken with a large quartz Littrow spectrograph, and c and d with a medium quartz spectrograph. Zn ,Na ~ EMISSION SPECTRUM OF ZINC OXIDE 315 could be identified with an observed spectrum were found in the examined region. Absence of the spectra is interpreted as a proof that Zn2 , ZnN, ZnH and ZnOH are not emitters of these bands. REFERENCES 1. F. L. Moh 1 er and H. R. Moor, J. Opt. Soc. Am. 15 (1927) 74. 2. J. M. W a 1 t er and S. B arr o t t, Proc. Roy. Soc. A 122 (1929) 201. 3. R. W . B. Pe a rs e and A . G. Gay don, The Identification of Molecular Spectra, 3-rd Ed., Chapman and Hall, London 1963. 4. A. G. Egerton and S . Rud r aka n ch an a, Proc. Rov. Soc. A 225 (1954) 431. 5. W. A. Parkinson, Proc. Phys. Soc. 78 (1961) 705. 6. J. A. De an, Flame Photometry, McGraw-Hill, New York 1960. 7. R. Herman und C. Th. J. A 1 k em ad e, Flammenphotometrie, Springer--Verlag, Berlin 1960. 8. N. S. Pol u et k o v, Metodi analiza po fotometrii plameni, Goshimizdat, Moskva 1959. IZVOD Emisioni spektar cink-oksida izmedu 6MO i 5000 A D. s. Pesic Koriilcenjem vakuumskog luka sa cink-elektrodama dobijena je grupa novih emisionih traka u zuto-zelenom delu spektra. Trake se proreduju prema crvenom delu spektra, ili pokazuju samo maksimume, i imaju difuznu strukturu pri srednjoj disperziji. Spektar je snimljen u atmosferi oksigena 16 i oksigena 18 pri snizenom pritisku. Kod vecine izmerenih traka utvrdeno je izotopsko pomeranje, pri zameni obicnog oksigena njegovim izotopom 18. Na osnovu dobijenih rezultata spektar je pripisan cink-oksidu. INSTITUT ZA NUKLEARNE NAUKE ~BORIS KIORIC« BEOGRAD Primljeno 13. jula 1966. 

Emission Spectrum of Zinc Oxide between 6000 and 5000 A

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