The strengths of the vibration—rotation lines of the first overtone, first hot band, and fundamental band of HBr have been measured by a curve of growth method, applying a correction for two overlapping lines devised by Sakai. The squares of the electric-dipole matrix elements |M02(m) |2 and |M12(m) |2 for the lines have been calculated, and have been fitted, respectively, to a cubic and quadratic polynomial in m, using the method of least squares. The experimental results for all three bands are compared with the theory of Herman and Wallis. The fact that the experimental |M02(0) |2 is less than that calculated from a linear dipole-moment function clearly requires a positive value of M2, the second derivative of the dipole-moment function.
The squares of the matrix elements |M01(0) |2 and |M02(0) |2 are used to calculate M1 and M2, the dipole-moment coefficients, for Morse and anharmonic oscillators. Of all the possible sets of M1 and M2 obtained in each case, the one giving results in better agreement with |M12(0) |2 is chosen. The chosen values of the dipole-moment coefficients are M1=+4.56×10−11 esu and M2=+0.69×10−3 esu cm−1 for the Morse oscillator and M1=+4.63×10−11 esu and M2=−0.70×10−3 esu cm−1 for the anharmonic oscillator. Since the sign of M2 is positive, the Morse oscillator results are preferred.
The equivalent widths, the line strengths, and the squares of the dipole matrix elements of the 2–0 vibration–rotation band lines of the H79Br molecule are measured. The measurements are made on a high-resolution infrared grating spectrometer which could completely resolve the two isotopic lines of H79Br and H81Br. This is the first time the high-resolution work on the intensities of the HBr molecule has ever been presented. The present data are compared with the earlier work obtained using a low-resolution spectrometer. It is found that the present values are considerably less than the earlier low-resolution values. The discrepancy between the two sets of results is attributed to the lack of resolution in the earlier investigations.
Vibration-rotation wave functions for HF and HI are computed by solving the radial Schroedinger wave equation numerically using an anharmonic potential function with seven adjustable parameters. With these wave functions the matrix elements of [(r - r
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