J. Quant. Spectrosc. Rodiat. Transfer Vol. 54, No. 6, 1035-1038, 1995 pp. zyxwvutsrqponmlk 0022-4073(95)00121-2 Copyright 0 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0022-4073/95 $9.50 + 0.00 zyxwvu DISSOCIATION ENERGIES OF PH AND PH+ R. R. REDDY, Y. NAZEER AHAMMED, A. SRINIVASA RAO, and T. V. R. RAO Department of Physics, Sri Krishnadevaraya University, Anantapur-515 003, India (Received 14 November 1994; received for publication 14 July 1995) Abstract-Dissociation energies for the ground electronic states of diatomic PH and PH+ are determined by fitting empirical potential functions to the respective RKRV curves using correlation coefficients. The estimated ground state dissociation energies of PH and PH+ are 3.10 and 3.20 eV respectively by the curve fitting procedure using Lippincott potential function. The computed values are in good agreement with experimental values. INTRODUCTION The potential energy curves are the characteristics of molecular states and form a convenient way of displaying energy levels of diatomic molecules. They play a major role in understanding the kinetic mechanism, spectral phenomena, stellar structure and other associated problems, such as ready application of Franck-Condon principle to radiative transition, dissociation and predissociation.’ However, data are lacking for the potential energy curves of the astrophysically important PH and PH+ molecules. Recent experimental work on these molecules has permitted the authors to take up this work. The A 3H-X3~ electronic spectrum of PH was first observed and assigned by PearseZ in 1930 from a continuous discharge through a mixture of hydrogen and phosphorous vapour. The spectrum of PH may occur in the Sun and cool stellar atmospheres. 3*4 The photoelectron spectrum of the emission spectrum of PH+ are known. 5*6 The literature concerning the spectroscopic properties of the PH+ ion molecule is rather limited. In view of their importance, dissociation energies for the ground states of diatomic PH and PH+ are determined by fitting empirical potential functions to the respective RKRV’ curves using correlation coefficients. CORRELATION COEFFICIENT It is possible to evaluate the dissociation energies of diatoms by fitting empirical potential functions to the RKRV curves using correlation coefficients.s-‘O The correlation coefficient is” where Xi represent experimental values of U used in the RKRV’ data and the yi are the corresponding values of U calculated by substituting rmin and rmax obtained from RKRV’ data into an empirical potential function. N is the total number of vibrational levels used. COMPUTATIONAL PROCEDURE Correlation coefficients between the estimated U and experimental RKRV’ values have been determined by varying the value of D, in steps of 0.1 eV around a selected value of D, . The value of D, giving the maximum correlation coefficient is selected for further refinement. This process is repeated in steps of 0.1 eV. The value of D, that corresponds to the maximum correlation 1035