• Sarvpreet Kaur

      Articles written in Pramana – Journal of Physics

    • Dissociation energy of diatomic molecules

      Sarvpreet Kaur C G Mahajan

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      The dissociation energy of twelve diatomic molecules has been determined by fitting four-parameter potential functionU(r)=De[[1−exp{−b(rre)}]/ [1−Cexp{−b(rre)}]]2 to the true Rydberg-Klein-Rees (RKR) curves for their fifteen electronic states using the mean square deviation as the criterion for the selection of the best fit. Average deviation ofDe has been found to be 2.7% as compared to 20.5% obtained with Lippincott’s potential function for these molecules. In addition the anharmonocity constantωexe has also been calculated for the same electronic states yielding average mean deviation 8.9%.

    • Wei Hua’s four-parameter potential: Comments and computation of molecular constants αe and εeXe

      Sarvpreet Kaur C G Mahajan

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      The value of adjustable parameterC in the four-parameter potentialU(r) =De [(1 - exp[-b(r -re)])/(1 -C exp[-b(r -re)])]2 has been expressed in terms of molecular parameters and its significance has been brought out. The potential so constructed, withC derived from the molecular parameters, has been applied to ten electronic states in addition to the states studied by Wei Hua. Average mean deviation for these 25 states has been found to be 3.47 as compared to 6.93, 6.95 and 9.72 obtained from Levine, Varshni and Morse potentials, respectively. Also Dunham’s method has been used to express rotation-vibration interaction constant (αe) and anharmonicity constant (ωexe) in terms ofC and other molecular constants. These relations have been employed to determine these quantities for 37 electronic states. For αe, the average mean deviation is 7.2% compared to 19.7% for Lippincott’s potential which is known to be the best to predict these values. Average mean deviation for (ωexe) turns out to be 17.4% which is almost the same as found from Lippincott’s potential function.

    • Some new four-parameter potentials and their use in the study of vibrational thermodynamical quantities of diatomic molecules

      Sarvpreet Kaur C G Mahajan

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      Three four-parameter potentials,UI,UII andUIII have been proposed and their accuracy has been demonstrated by finding the mean square deviation from the true RKR potential curve for 15 electronic states of 12 diatomic molecules. Their percentage average mean square deviations from RKR curve have been found to be 1.45, 1.86 and 2.89, respectively. These compare favourably with the value 2.67 for the recently suggested four-parameter potential of Wei Hua which itself yields better results than the commonly employed three-parameter potentials. The superiority of the new potentials (especially ofUI andUII has been further established by using these potentials to calculate the molecular constants αe and ωexe following Dunham’s method. The corresponding percentage average mean deviations, for αe, turn out to be 3.75, 5.13 and 15.43 and for ωexe 8.73, 17.23 and 27.49, respectively, against the respective values of 7.97 and 18.88 with Wei Hua’s four-parameter potential. Also included are the values of dissociation energy determined with these potentials and these too corroborate the better performance ofUI andUII. The relative worth of various potential functions has been further tested by carrying out numerical study of vibrational partition function (evaluated by sum over states method), entropy and thermal capacity for the ground state of 7 molecules and comparing these with the corresponding findings based on the RKR data.

    • Universal relation between spectroscopic constants

      Sarvpreet Kaur C G Mahajan

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      A universal relation between the Sutherland parameter, Δ (= kere/2/2De) and the dimensionless parameter G (= 8ωexe/Be), has been established using 40 electronic states, which include ground as well as excited states of polar and non-polar molecules. This relation is used to predict the dissociation energy of four lowest electronic states of S2 molecule. The respective values for the states X3Σg/−, a1Δg, b1Σg/+ and B3Σu/− turn out to be 36557, 31431, 28247 and 13429 cm−1, and are in good agreement with the experimental values. Furthermore, metastable states a1Δg and b1Σg/+ of S2 are shown to dissociate into 3P1 + 3P1 as against the dissociation of X3Σg/− into 3P2 + 3P1. In addition, a relation between Sutherland parameter Δ and internuclear distance re, viz., Δ=2.2re has been obtained for the ground state of alkali diatomic molecules.

    • Response to the comment on: "Universal relation between spectroscopic constants"

      Sarvpreet Kaur C G Mahajan

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