Behere, S H

Bhartiya, J B

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IndianJ. fhys. MB (2), 129-132 (1990)Dissociation energy of CrF moleculeJ B BhartiyaDepartment of Physics, S B College of Science, Aurangabad-431 001, India andS H BehereDepartment of Physics, Marathwada University, Aurangabad-431 004, India Received 1 August 1989, accepted 12 December 1989Elements in the middle of the periodic table i.e. transition metals yield complex spectra. Naturally, the molecules involving these elements also give complex spectra due to transitions in the electronic states having high multiplicities. Few efforts were made to resolve their spectra and carry out the analysis but they were hardly successful and as a result molecular constants of such molecules were not reported. Diatomic chromium fluoride CrF is an example whose molecular constants are known quite recently.The spectrum of CrF was reported earlier by Durgavati and Rao (1954). They estimated the ground state frequency around 536 c m '' .  Dubov and Shenyavaskaya (1987), recently reinvestigated the CrF rrolecule in emission as well as in absorp­tion and reported the molecular constants of A ® Z '-X “s  transition. These constants used in present work, are shown in Table 1. They also confirmed the identity of emitter by using various compounds. However, the bands observed by Durgavati and Rao (1954), were not observed by Dubov and Shenyavaskaya (1987). This may be due to the reason that the ground state frequency 662.3 cm" ^  of CrF reported by Dubov and Shenyavaskaya differs from that of Durgavati and Rao (1954).The evaluation of dissociation energies of diatomic rrolecules is of fundamental importance in thermochemistry and astrophysics. Huber and Herzberg (1979) The present investigation deals with the estimation of the value of D* by fitting the empirical potential function to the Rydberg (1931), Klein (1932), Rees (1947) and Vanderslice.et ol (1960) RKRV curve using correlation coefficient method suggested by Rao et al (1981, 1982).Many empirical potential functions are known for diatomic molecules. Of these, the function given by Hulbert-Hirschfelder (1941, 1961) and Steele and Lippincott (1961), have been used. In the present study, the RKRV curve of theX "!; state of CrF is constructed using the molecular constants reported by Dubove 129130Table I. Molecular constants for the ground state x "S  of CrF (Dubov and Shenyavaskaya, 1987).j  B Bhartiya and S H BehereO), u>,X, B, 4?(cm *) (cm ')  (cm *) (cm ')r.(A)662.3 3.4 0.379*from Pekeris relation0.002596 1.785and Shenyavaskaya (1987). The classical turning points and corresponding Urkr values are presented in Table 2. The H -  H potential function which is used to estimate the dissociation energy is of the formTable 2. Potential energy curves of CrF molecule (turning points).whereV' u(cm ’ )fmin ('^) fmiix (A)0 330.29 1.728 1.8491 985.79 1.689 1.9002 1634.49 1.664 1.9383 2276.39 1.645 1.9704 2911.49 1.625 1.9995 3539.79 1,614 2.0266 4161.29 1.602 2.0517 4775.99 1.591 2.0758 5383.89 1.580 2.099UHH(r) = D,(8065.48)i(1 l cx”e“ “• ' ( H - M l (1)Og is in eV.x=^[o,,/2(8065.48 B ,D , ) l ] [ ( r -  r „ ) / r j0(1— : 0, = -  1 -  (•CjW^  'eBj)o ,= r(5 /4 )o “ ~ (2w^x„/3BJ b - 2 - j t ( 7 /1 2 ) - ( 8 0 6 5 .4 8  D ,).o ,/o „]/c ( c -  [1+ O i(80 65 .48 D ,.o .,/fl„ )f]The r„„n and values obtained from RKRV calculations are substituted in eq. (1) and corresponding U{r)  values are calculated for different vibrational levels uBing anDissociation energy of CrF molecule 131arbitrary value of Dg. These values of U(r) are compared with Urkrv values to obtain a correlation coefficient. In the first stage, D , values are varied from 1 eV to 6 eV. A  good correlation is seen around 4 eV. In order to obtain a better correlation, D , values are again varied from 3.0 to 4.3 eV in steps of 0.01 and correlation coefficients are obtained for each D , value. The Dg that corresponds to the maximum correlation coefficient is taken as the best value of Dg.The values of correlation ceofficients obtained from H -  H potential functionle 3. It is seen from the table thecurve are presented inTable 3. Correlation betweenHulbert-Hirschfelder function and true potential energy cur­ves of CrF-X ‘ state.Dy (eV) Correlationcoefficient1 0.96448872 0.99883943 0.99994924 0.99999295 0.99997936 0.99997113.0 0.99994833.1 0.99996453.2 0.99997463.3 0.99998233.4 0.99998743.5 0.99999153.6 0.99999263.7 0.99999453.8 0.99999423,9 0.99999414.0 0.99999204.1 0.99999154.2 0.99998944.3 0.9999891on energy (D j) obtained inmaximum cm-elation coeHiciem uaiug H - H  function is 0 .9 9 9 9 9 « . HowaVM, fo, the same D . value <x.„esp<mding value of conelatmo ™ « , o »  Lippincott potential function is 0.9989134. We conclude that the H -  H f u t « ^  gives bette, fit  to RKBV cun» of X T  smte of O F . The value of D .(4 .S ! 1 0.20) teponed eadie, by Kent and Marorave (1966), is bas«l on mass spectrometnc stuches that temained unconfitmed by spectroscopic method. The percentage132 J B Bhartlya and S H Beherecharacter (1C) of CrF is calculated from electronegativities of their constituent atoms, using expressions given by Hannay and Smith (1946), Pauling (1952), Wilmshurst (1959), Batsnov and Durakov (1961) which is presented inTable4. The average value of 1C comes around 58% ; which indicates that the molecule is ionic in nature andTable 4. Electronegativities and percentage ionic character (1C) for CrFmolecule.Hannay BatsnovXp ~ Pauling Wilmshurst andSmyth Durakov(1946) (1952) (1959) (1961)5.6 2.4 58.56 64.54 42.85 68.39Xa and Xg are electronegativities of the constituent atoms.hencethe ionic binding dominates over covalent binding. TheD" of chromium chloride and bromide are reported by Rao and Rao (1949), Rao (1949) and Bulewicz et al (1961) as 3 .7  eV and 3.3 eV respectively. But these thermochemical values a^e based on flame photometric studies. Since there is no other report of on CrP, for spectroscopic work, the value suggested in present work may be used.AcknowledgmentWe thank Dr M  L P Rao for his interest in present work and helpful correspondence.ReferencesBatsnov S S and Durakov V I 1961J. Struct. Chcm, 2 424Bulewicz E M, Phillips J G and Sugden T M 1961 Transact raraday Sac.  57 921Dubov V M and Shenyavaskayo E A 1987 Opt. Spectrosc. 62 1 95 *Durgavati B K and Rao V R 1954 Ind.J. Phys. 28 525 Hannay N B and Smyth C B 1946J. Am. Chem. Sac. 68 171Huber K P and Herzberg G 1979 Constants of D/otom/c/Vlofecufes. (New York : Van Nostrand Reinhold Company)Hulbert H M and Hirschfelder J 0  1941 J, Chem. Phys. 9 61 ------1961 J. Chem. Phys. 35 1901Kent F and Margrave J L 1965 J. Am. Chem. Soc. 87 3582Klein 0  1932 Z. Phys. 76 226Pauling L 1952 J . Phys. Chem. 56 361Rao V R and Rao K R 1949 Ind. J. Phys. 23 508Rao V R  1949 Curr. Sci. 18 338Rao V M, Rao M L P and Rao P T 1981 J. Quant. Spectrosc Radiat. Transfer 25 547-----1982 Phys. Rev. A 26 1765Rees A L G 1947 Proc. Phys. Soc. 59 998Rydberg R 1931 Z. Phys. 73 376Steele D and Lippincott E R 1961 J. Chem. Phys. 35 2065Vanderslice J A, Mason E A, Maisch W G and Lippincott E R 1960 j .  Mol. Sfiectrosc. 5 83 Wilmshurst J K 1959J. Chem. Phys. 30 561

Dissociation Energy of CrF Molecule

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Dissociation Energy of CrF Molecule

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