Lakshman, S V J

Venkataramanaiah, M

English

IACS Institutional Repository

21THE EMISSION BAND SPECTRUM OF AsOM. VENKATAHAMANAIAH ai^  S. V. J. LAKSHMANS p e c t r o s c o p i c  L a b o r a t o r i e s ,  D e p a r t m e n t  o f  P h y s i c s ,Sri Vei-tkateswaba Ujfivi^aiTY, Tiropati.(Received January 24, 1904; RtaxAmiiiled, April 6, 1964).Plate VIIABSTRACT. Thf' band Hpt’iotrum of AsO exoited in a heavy current, discliargo run on a 2000 voit, 1 ampere transformer, revealed a large number of new bands in the region X 4100 -X.3400A. They have been analysed into two systems. The lower state frequency for both th(‘sf* systems has been found to be eiiual to the ground state frequeivy of the mole­cule, The mole(!uIar constaixts found for thes« two systems are summarised below;i;' Y IT — 27095.5 I’m'’ t ,L-X-lIr;F« .-2(jsQ2.,5r,n-< ’ 714 pm~iXc' w/ =  2.5 m -i ; u«" =  96,1 om'i x ," =  4.5 pm"!F -X2IL  : ««" {>64 cm-i; ««’ e» 689 cm->I N T R O D U C T I O NIn an earlier publication on this molecule, Lakshman ami Rao (1960) reported two new doublet band systems designated as C*A — Z^ II,. and Z>(®II ?)—Z-II, in the region A3100—A2400A. Prior to this, Connelly (1934), Jenkins and Strait (1935), Shawhan and Morgan (1935), all about the same time reported indepcn- dantly two doublet systems A -X  1^1 and B  X *n of AsO. in emission, in various sources of excitation in the region A 3450—A2350A. All these four systems reported namely, A — X ,  B — X ,  0 — X ,  and D — X .  have a common lower *11^  state, with a doublet splitting of 1026 cm~^ Connelly’s absorption experiments proved this lower system as the normal ground state of the AsO molecuh'.The investigations on this molecule have been continued in order to obtain a band system analogous to the A  *11—X®n system, earlier found in SbO by Mukherji (1931), Sen Gupta (1939), Lakshman and Rao (1960), and Shimauclu (1960), This work has led to the analysis and identification of two new systems designated as E — X  *11, and F ~ X  ®n, in the band spectrum of the AsO molecule. The present paper deals with a detailed analysis of the bands of this system.209E X P E R I M E N T A LExperimental proc edure adopted in the present investigations waft the same as reported tsarlier by Laksliman and Kao (I960), except that a 2kv transformer had been used instead of a 4kv transformer. The bands are so very feeble in intensity, that exposures varying from 20 to 45 minutes were found necessary to phot(^graph them on Ilford Special Raind, Ilford Panchromatic and Agfa Isopan Superspecial plates using a Hilger Medium Quartz Spectrograph. Wavelengths of the band heads were made using iron arc lines as standards. The vacuum wave numbers were obtained from Kaysor’s tables.210 M . Venkataramartaiah and S. V. J. LakshmanB E  S U L T  SNew bands obtained in the region A4100—A3400A are reproduced in })late VII. Though the bands are sharp they are so very feeble in intensity that all our attempts failed to photograph them with reasonable intensity on a larger Littrow Spi^ctrograph.The new red degraded bands start from th(^  long wave length side? of the A —X  system, i,e. about A3400A and extend upto nearly /\4100A. It was at first thought that they could be the extension of the A — X  system. Our attempts to fit them into the vibrational scheme of tlie A ~ X  system were not successful. Therefore, it was concluded that they might fall into one or more separate systems. The wave length, w^ ave number, intensity and classification of these band heads are all given in tal>le I.system. :Bands with heads at A3628.8, A3659.8, A3690.5A appear to form ono sequence with a wave number interval approximately equal to 235 cm~ .^ Similarly another sequence of bands could be picked up with heads at A3510.2, A3541.1, and A3570.9A, giving almost the same wave number interval. Further a wave number interval equal to 931 cm i is found between the bands at A3510.2 and A3628.8A. This is close to the value of the lower X  state of the AsO molecule. Takingthis as a clue, the other bands as far as they could, have been picked up to fit into a vibrational scheme as shown in Table II.The rest of the bands could very well be fitted into two components of a doublet system, with a doublet interval of 733 cm~  ^in the upper state. Therefore it is quite propable to assume that the other component of this F —X  F^L system has not been excited in the mode of excitation adopted by the authors. The approximate vibrational constants of this system are given hereunder :o>V f689cm“'i; 964 om-^The Em ission Band Spectrum o f AsO  TABLE I2X 1Wavo length, Wave number, Intensity and Vibrational assignmcmts o f the bands o{ E —X  I^T and F —X ^ Il systemsX A V cm“ i Intensity Assigment3521.83651.43611.4 3706.3 3740.6 3842.1 39H7.128386281482768226973267262602025074E-^X2n:i/.2,03.1 1 , 0  0,01.1 0,1 0,23650.5 27386 2 1,03682.3 27149 2 2,13747.1 26680 1 0,03920.8 25498 1 1,24032.7 24790 1 0,2F ^ x m3428.0 29163 2 (V'4-2,2)3479.0 28736 2 V'. 13510.2 28480 5 V '+ l , 23541.1 28232 3 V '-f 2, 33670.9 27996 4 V'+3,43596.9 27794 4 V'. 23628.8 27549 4 V - f l , 33669.8 27316 3 V'4-2, 43690.6 27089 2 V'H-3, 6TABLE HVibrational Scheme of the band heads of the F —X  system o f AsO212 M . Venkataramanaiah and 8 . V. J . LakshmanV"V'0 1 2 3V' 28730 942 27794686V '^ i 28480 931 27549683 683V'-f 2 29163 031 28232V'+36802799C 907 27089E —X  ‘^ 11 systemTable III gives the DesJandre’s sdK i^ne for the two components of this system. The band heads of the two coTnjionents of this system could be represtmted by the quantum formula :V -  -| -7 1 4 (r+ J )-2 .5 (F '-t -ir -!)6 3 (r|to within an accuracy of 3 eni~ .^TABLE IIIVibrational scheme of the band heads of the E —X  Hi system of AsO. V" V'  ^ . 0 1 20 26973 9.53 26020 946 2507426680 — — — 24790709 — 706 — —706 — — — 7087 27682 956 26726 — —27386 — — — 25498704 — — — —— — — — —2 28386 — — — —— — 27149 —3 — •— 28148 — —— — — — —VENKATARAMANAIAH & LAKSHMANIndian Journal o f  Physics, Vol. XXXVm, No. 4P L A T E -V IIMedium Quartz Spectrogram The new E-X & F-X Systems of AsOThe Emission Band Spectrum of AsO 21$D I S C U S S I O NThe ground state electron configuration for the AsO molecule can be written in MuUiken’s notation as i[ Z a f  { Y c r ) ^ m T f  {£on |(Fn)A study of the ionised spectra of molect|tes gives us a clue to know which of the two bunding orbitals (xo") or (toH) is po^ssing higher energy than the other. As n  state has been observed as the first exceed state in the case of NO+ and NS+ we may expect for molecules with small in|smuolear distance o il orbital to lie inside the xcr orbital. As state has beei| observed as the first excited state in the case of PO+, PS+ and AsO+, we may ^peot for molecules with large inter- nuclear distance x <t orbital to lie inside the orbital.The states E  and F  may then be expected to belong to the following con­figuration.(Z(T)^Yaf (x(r)2(un)»(V n)*..... 2n<, *n, niiThe E — X  system may belong to a E ^ H r — X  ®IIr transition with a splitting of 733 cm~  ^ in the upper E  state. Similarly the F — X  system may belong to a f  *n— transition with upper state belonging to Hund’s cas(5 (b). The nature of the states can however be only confirmed on the basis of a detailed rotational analysis.A C K N O W L E D G E M E N TThe authors wish to express their grateful thanks to Professors P. Tiruven- ganna Rao and K. R. Rao both of the Andlrra University for their interest in thift work. The authors thanks are also due to the authorities of this University for placing aU the equipments necessary for this w'ork, at their disposal. One of the authors (M.V.R.) is grateful to the C.S.I.R. (Delhi) for a Junior Research Fellowship.R E F E R E N C E SConnelly, F. 0., 1934, Free. P h y . Soo., London A , 48, 790.Jenkins, F. A., and Strait, L. A., 1935, P. B„ 47, 136.Lakshmsn, 8. V. J., and Tiruvenganna Rao, P., 1980, In d , J ,  P hy. 84, 278.Morgan, F., and Shawhay, B. N., 1935, F. R.. 47, 192.Morgan, F., and Shawhay, E. N., 1935, F. B ., 47, 199.I^mauohi, Midori, 1960, Seienee of Light (Japan)., 9., 109.

The Emission Band Spectrum of AsO

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The Emission Band Spectrum of AsO

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