Molecular Constants of Cesium Chloride by the Molecular Beam Electric Resonance Method

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Abstract
The electric resonance method of molecular beam spectroscopy was used to observe the CsCl spectra arising from transitions of the type J,mJ →J,mJ′, where J is the rotational quantum number and mJ the electric quantum number. The following transitions were identified and studied : 2,0→2,1;3,0→3,1;4,0→4,1;4,1→4,2; and 5,1→5,2. An analysis of the spectra for several values of the electric field intensity gave the following molecular constants for the ground vibrational state of Cs133Cl35: μ0=10.46±0.14 debye; A 0=(385±9)×10−40 g cm2; B 0=(72.7±1.7)×10−3 cm−1; r 0=(2.88±0.03)×10−8 cm. μ0 is the electric dipole moment,A 0 is the moment of inertia, B 0 is the rotational constant, and r 0 is the internuclear distance. If μ is assumed to be proportional to the internuclear distance, and if the potential function is assumed to be a cubic, then the vibration‐rotation constant α e is calculated to be (0.53±0.08)×10−3 cm−1. From measurements of line widths it was possible to set upper limits on the quadrupole interaction constants of Cs and Cl; viz, |eqQ/h| Cs ⩽4 mc/sec and |eqQ/h| Cl ⩽3 mc/sec .