Gopal, R

Joshi, M M

Uttam, K N

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Indian J . Phys. MB (6), 468-474 (1990)Thermal emiBsion spectra of the NiF molecule in the region AA 4500 — 4850 AR Gopal, K N Uttam and M M JoshiPhysics Department University of Aliahabad, Aiiahabad-211 002, India Received 6 February 1990, accepted 21 August 1990Abstract: Thermal emission spectra of the NiF molecule have been photo­graphed in the wavelength region AA 4500-4850 A on a reciprocal linear dispersion of 3.5 A/mm. Out of 60 bands recorded 45 are new ones. These bands have been classified into four systems viz. A 4518 A, A 4675 A, A 4700 A and A 4550 A. The vibrational constants have been obtained for the first three systertis and the vibrational analysis of the system A 4518 A has been confirmed byl observedisotopic shift due to nickel. 1Keywords : NiF molecule, thermal emission, optical spectra, vibrational cons­tants.PACSNo: 33.20. kf I , In troductionThe band spectra of NiF molecule was first photographed by Krishnamurty (1953) on low resolution using high frequency discharge in the region AA 4578-4860 A. He reported three groups of bands, each consisting of 4, 5  and 4  bands lying at x 4518 A, A 4675 A and A 4700 A respectively and assigned all these bands to a single system. Pinchemel et ol (1979) on the basis of rotational analyses of bands at A 4518 A and A 4700 A attributed them to the transition. LaterPinchemel (1981), on the basis of rotational analysis, suggested that the band A 4675 A belongs to the transition *77-*S+ and the ground state of NiF is Gopal and coworkers (Gopal and Joshi 1981, Gopal et al 1981) have studied thermal emission spectra of NiF at low resolution and obtained 4 and 5 new sub­systems in the regions AA 4650-5125 A and AX 4100-4430 A respectively. Recently Bai and Hilborn (1986) on the basis of L. I. F. studies suggested that the ground state of NiF molecule isPresent investigations have been carried out with a view to have more detailed spectroscopic information regarding the NiF molecule using thermal emission technique.468Thermal emission spectra etc 4692. Experim entalA  small quantity of anhydrous nickel fluoride (Alfa-Ventron) mixed w ith  spec-pure nickel metal powder kept in experimental tube of Saha's high temperature furnace (Saha et al 1927) was heated electrically at about 2400 C in an atmosphere of argon at about 60 torr. Exposure of about 5 and 10 minutes was found 'sufficient to record good spectrogram on ORWO-400 ASA film on a Carl Zeiss Ebert Plane Grating Spectrograph PGS-2 w ith  grating blazed at A 5600 A and total lines 45600  on a reciprocal linear dispersion of about 7 A/mm and 3.5 A/mm respectively. Spectrum of Cu was used for comparison. Measurements were done on Carl Zeiss Abbe comparator w ith  a least count of 0.0001 mm.3. ResultsThermal emission spectrum of NiF molfK:ule has been reproduced in Figure 1. While intense part of the spectrum lies in the region AX 4500-4700 A , a group10.01.0SybtpmQfc010,0a s :R ffAORecFigure L Thermal emission spectrum of the NiF molecule in the region AA 4500-4700 A.of weaker bands also lies on XA 4841 A. Following are vibrational analyses suggested by the authors :3.1. System X 4518 A ( ' * 7 7 ^ , * - *  tronsition) :Two groups of bands lying at A 4518  A and A 4662 A consisting of 15 and 13 bands have been classified as j v  =0 and = - 1 sequences respectively. The7A470 R Copal K N Uttam and M M joshibands are red degraded and Q heads are found to ^  stronger than the R heads. Isotopic shift due to nickel observed in case of 7 bands of — 1 sequence justify our analysis. Out of these 28 bands 22 are new ones. The vibrational constants obtained for this system are as follows :22141 R 2 2 1 2 5 Q \  <Oe 692.98, w'.x'J -3 .9 9 , -6 9 6 .2 0and fo'^Xg -- 3 .85.Table 1 is the collection of the band head data, visual estimates of intensities andTa b le  I. Band-head data for the system A 4518 A.in cm ' Int. (V . V") .^.hs in cm * Int. . V")22125.5 22125.0 7 0. 0 Q* 21491.0 21491.3 3 3, 4 R22128.5 22128.5 6 1 . 1 Q* 21493.9 1 3. 4 R‘22132.0 22132 3 4 2, 2 Q* 21504.0 21503.6 2 \^ 4, 5 R22141.0 22141.0 6 0, 0 R* 21506.7 1 Y  5 R«22144.5 22144.5 5 1 , 1 R* 21517.0 21516.2 2 6, 6 R22148.2 22148.3 4 2, 2 R* 21519.6 1 5* 6 R‘22152.0 22152 4 4 3. 3 R 21529.8 21 529.1 2 6, 7 R22157.0 22156.7 3 4, 4 R 21543.2 21542.3 2 7, 8 R22161.6 22161.2 3 5, 5 R 21556.0 21555.7 1 8, 9 R22166.6 22166.2 3 6. 6 R 21570.0 21569.4 1 9, 10 R22171.5 22171.4 2 7. 7 R 21584.3 21533.4 1 10, 11 R22176.5 22176 9 2 8. 8 R22181.9 22182.6 2 9, 9 R m22187.7 221B8 6 1 10, 10 R Nickel Isotope Effect22193.0 22194 9 1 1 1 , 11 R in ir.cm“ ' cm*'21440.7 21440 0 5 0, 1 Q 0, 1 Q 2.95 3.321444.0 2 0, 1 Q' 0, 1 R 2.95 3.421451.5 21451 5 4 1. 2 Q 1,2 R 2.90 3.121456.0 21456.0 4 0, 1 R 2, 3 R 2.84 3.021459.4 2 0. 1 R' 3, 4 R 2.78 2.921467.2 21467.5 3 1 . 2 R 4, 5 R 2.73 2.721470.3 2 1 ,2  R^ 5. 6 R 2.68 2.621479.0 21479.3 3 2. 3 R21482 2 2, 3 R'‘Denotes bands due to ’Ni '"F molecule.*Bands reported by Pinchemel et al (1979).thair classifications. A comparison of isotopic shift w ith those of calculated is also shown in Table 1.Thermal emission s|>ectra etc 4713.2. System A 4700 A transition) :Three groups of 12 bands lying at about A 4557 A, \  4700 A and a 4841 A have been analysed as 40=  + 1 , 0 and - 1  sequences of the system. It includes 6 band heads lying at A 4700 A attributed to 4 v = 0  sequence by Pinchemel et al (1979}- In this case also the Q heads are found to be stronger than the R heads. The vibrational constants for the system are as below,21294.5 R„Vo,o =  21288.2 Rficm"^, dG'i,*=644 .7  cm"^ and J G 'i„= 64 2  cm■^ 21274.7 Q»,Table 2 displays the band head data along with visual estimates of their intensities and classifications.Table 2. Band-head data.o^ba Peal in cm’’' Int. (v'a y") bttti in cm'^ Int. V")System 4700 A System 4675 A20630.0 20630.0 2 0* 1 Qle 21384.6 21384.6 4 0,0 0*20643.4 20643.5 1 0. 1 Rrr 21388.7 21388.7 6 0, 0 R*20650.0 20649.8 1 0, 1 Ree* 21390.4 21390.9 3 1,1 Q21274.7 21274.7 7 0, 0 Q(t» 21394.5 21395.0 5 1, 1 R21268.2 21288.2 5 0, 0 Rif# 21403.0 21403.0 4 2, 2R21294.6 21294.5 5 0, 0 Rec# 21413.1 21412.7 4 3, 3R21273.6 21272.0 6 1r1 Qfe# 21423.5 21423.0 4 4,4R21286.7 21285.5 4 1 . 1 Rfi# 21434.2 21436.1 4 5, 5R21291.8 21291.8 4 1 Ret* 22073.1 22073.1 1 1 , 0 021916.5 21916.7 2 1, 0 Qf, 22077.2 22077.2 2 1,0R21930.3 21930.2 1 1,0 Rf,21936.4 21936.5 1 1c 0 R.C Unclassified bandsSystem 4550 A 21935.021943.03321972.1 6 OcO 21951.6 221976.7 6 I r l 21954.0 221980.0 4 2,2 21985.6 221995.1 1*Bands reported by Pinchemel et al (1979,1981).3.3. System A 4675 A ( ‘/J,,* -  *1^ * transition) :A group of 8  strong bands lying at A 4675 A  has been classified as 4 o= 0  sequence. It includes three bands reported as (0, 1) by Krishnamurty (1953) which later onwas classified as 4 v = 0  sequence by Pinchemel (1981). A faint band lying atA 4628 A has been attributed to this system as (1, 0). In this case R heads are found to be stronger than the Q heads. The vibrational constants obtained for the system are as below.OiQQQ 7 p*'o.o ~ 2 1 3 8 5 .0  *'‘*’a=‘ 691 .6 , w#x ', '= 4 .7 ,w’* = 696.2  a n d 3. 85The band head data along w ith  visual estimates of their Intesities have been collected in Table 2.3.4. System A 4550 A  :It  consists of three strong bands attributed to j v = 0  sequence along w ith  few  weaker bands lying both the sides of these bands and are left unclassified. The band-head data has been mentioned in Table 2.4. DiscussionThe earlier workers on the basis of low resolution studies of NiF spectra, \Classi- fied the tw o  group of bands lying at A 4518 A and A 4675 A as and j i  =  -  1 sequences respectively and the vibrational frequency for ground state had been found to be 740 cm~^. Recently Pinchemel (1981) on the basis of rotational analysis reassigned the group of bands lying at A 4675 A as j r —0 sequence of a new system. A  comparison between the vibrational frequencies m obtained from present vibrational analyses and an approximate value of vibrational frequencies (Herzberg 1950) calculated from the rotational constants B and D using relationD =  ~  has been compiled in Table 3. It is clear from the table that the order ofmagnitude of cu, determined from vibrational and rotational data are almost the same for various electronic states. The comparison of £«y for NiF, NiCI and NiBr also justify the ground state vibrational frequency of the NiF molecule. This value is also consistent w ith  those observed in the ground state of similar molecules (for example : 640 cm” *^ in the X * i7  state of CuO).Pinchemel et al (1979) on the basis of rotational studies proposed that the transition responsible for the bands A 4618 A and x 4700  A are “ and»77 i,a -*Js ,9  respectively. Later on Pinchemel (1981) attributed the band A 4675 A x o ^ U -^ E *  transition and suggested ^E* as the ground state of NiF molecule. Recently Bai and Hilborn (1986) on the basis of L.I.F. study and measurement of decay time of fluorescence of bands A 4518 A and X 4675 A of NiF molecule proposed that both the bands arise from the same upper state ’‘7 7 ,/, and * r +  lies about 740 cm~^ above the ground state which is contrary toPinchemel's suggestion (1981). In present observations authors have found that the first vibrational quanta in the upper state of the tw o band system A 4518 A and472 R Copal K N Uttam and M  M Josh IA 4675 A are of the same order. Thus authors' observations are in support of Bai and Hilborn's suggestion (Bai and Hilborn 1986).Thermal emission spectra etc 473Table 3. Spectral data of NiF molecule.State To in cm"' B, DoxlO' cm"Presenttue in cm"''^a/3 22125 0.3792 3.7 768 69621645 0.3772 4.0 733 p^646740 0.38567 4.9 684 691.6’■ 4.,, (X,) 370 0.3861 4.6 707 P5^ 650(X.) 0 0.3886 3.5 819 693Molecule NiF NiCI NiBrwj in cm“  ^ (XJ 650 433.9 310.0(Xi) 693 427.1 322.7Doublet separation 370 484 633(JX) in cm~**An approximate vaiue of (Herzberg 1950).caicuiated from rotationai constantsThe rotational studies of NiH reveal that the ground state of NiH molecule is (Huber and Herzberg 1979). Rao and Rao (1969), Darji and Suresh Kumar(1989) and Darji (1989) on the basis of rotational studies found that ground state of NiCI is Considering the analogous case of NiF, in light of above facts, it is reasonable to assume as the ground state of NiF molecule as suggested by Baiand Hilborn (1986).AcknowledgmentsThe authors are thankful to late Prof B K Agarwal and Prof S K Kor for their keen interest in this work. RG is also grateful to UGC, New Delhi for the financialsupport.ReferencesBai J and Hilborn R C 1986 Chem. Phys. L e tte rs  IJ8133Darji A Band Suresh Kumar 1989 Indian.). P.;re/ipp/.PhKs. (In press)Darji A B 1989 Second IPA/DST S ym pos ium  on Lasers a nd  A p p lic a tio n s ,  (B. H .  U  ,  V a ra n a s i)  p 197 Gopal A and Joshi M M 1981 Curr. Sci. 50 530Gopal R, Singh L K and Joshi M M 1981 Indian). Phys. S5B 507Herzberg G 1950 Molecular Spectra and Molecular Structure Vol I. Spectra of Diatomic Molecules(New York: Von-Nostrand) p 105 .. . jHuber K P and Herzberg G 1979 Constants of Oiatorrric Molecules (New York: Van NostrandRelnhold)4 7 4 R Copal K N Uttam and M M Josh!Krlshnamurty V 6  1953 I n d i a n  J .  P h ys . 27 354PInchemel B, Lefebvre Y and Schamps J 1979J. M o l .  S p e c t r o s c . 77 29 Pinchemel B 1981 J .  P h ys . B ; A t .  M o l .  P h ys . 14 2569 Rao N V K and Rao P T 1969 C u r r ,  S c i .  f l n d . J  3B 689 Saha M N. Sur N K and Majumdar K 1927 Z. P h y s .  40 648

Thermal Emission Spectra of the NiF Molecule in the Region λλ 4500-4850 Å

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Thermal Emission Spectra of the NiF Molecule in the Region λλ 4500-4850 Å

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