The Rotation / Vibration Spectrum of HCl

Index

Introduction

Quantum Vibration and Rotation

Electric Dipole IR Transitions in Molecules

Experimental Procedure

Calculations and Discussion

CALCULATIONS AND DISCUSSIONS

• Assign the lines (as in Fig. 1) in the HCl and DCl spectra. Measure (cm^-1) as accurately as possible, tabulate with the corresponding m values, and calculate (m).
• Plot these data according to Eq.(8) and by linear least-squares find (2_e-3_e) and (2_e), and then _e and _e.
• Find _o from Eq. (7).
• Tabulate these parameters for HCl and DCl (in cm^-1), as well as I_e and R_e. (Remember that exact masses for the isotopes should be used and not just the mass of mixed naturally-abundant isotopes; for example, m_D = 2.014102 amu.)
• Calculate the ratios _o(DCl)/_o(HCl) and _e (DCl)/ _e(HCl) and compare them with the "harmonic" values given by Eqs. (9) and (10).

REFERENCES

1. P.W. Atkins, Physical Chemistry, (5th edition), Freeman, NY, 1994, pages 574-6.

2. J.D. Graybeal, Molecular Spectroscopy, McGraw-Hill, NY, 1988, Chapter 12, page 332ff.

3. The authoritative sources for the spectroscopy of all diatomic molecules (up to about 1979) are the two books: G. Herzberg, Molecular Spectra and Molecular Structure I. Spectra of Diatomic Molecules, (2nd edition), Van Nostrand, New York, 1950 and K.P. Huber and G. Herzberg, Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules, Van Nostrand Reinhold, New York, 1979.

4. P.R. Griffiths, Fourier Transform, Infrared Spectrometry, Wiley, NY, 1986.

5. L. Glasser, J. Chem. Educ., 64, A228, 260 (1987).

This document originates from the notes of W. Weltner, Jr.

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