Hyperfine Structure in the Microwave Spectrum of HDO, HDS, CH2O, and CHDO : Beam-Maser Spectroscopy on Asymmetric-Top Molecules

Abstract

Hyperfine structure in the 2₂₀→2₂₁ rotational transition of HDO at 10 278.2 Mc/sec and HDS at 11 283.8 Mc/sec, and in the 2₁₁→2₁₂ rotational transition of CH₂O at 14 488.6 Mc/sec and CHDO at 16 038.1 Mc/sec, has been investigated with a high‐resolution beam maser microwave spectrometer. Linewidths of 5 kc/sec have been obtained. The hyperfine Hamiltonian for an arbitrary number of nuclei with quadrupole, spin—rotation, and spin—spin interactions is discussed, and the matrix elements of the Hamiltonian and the intensities of hyperfine transitions calculated in terms of the tabulated 6j coefficients. Quadrupole and spin—rotation constants and bond lengths which have been determined are, for the 2₂₀ state of HDO: (eq_JQ)_D = 79.3±0.3 kc/sec, C_H = —43.47±0.11 kc/sec, C_D = —2.33±0.02 kc/sec; for the 2₂₁ state of HDO: (eq_JQ)_D = 79.6±0.3 kc/sec, C_H = —43.63±0.13 kc/sec, C_D = —2.20±0.02 kc/sec; for the 2₂₀ state of HDS: (eq_JQ)_D = 42.9±0.4 kc/sec, C_H = —25.03±0.13 kc/sec, C_D = —0.47±0.02 kc/sec; for the 2₂₁ state of HDS: (eq_JQ)_D = 43.3±0.4 kc/sec, C_H = —25.45±0.13 kc/sec, C_D = —0.22±0.02 kc/sec; for CH₂O: C_H (2₁₁) — C_H (2₁₂) = 2.26±0.13 kc/sec, C_H (2₁₁) = 0.65±0.50 kc/sec, 〈1/r_HH³〉^—⅓ = 1.898±0.017 Å; for CHDO: (eV_ξξQ)_D = 170.0±2.0 kc/sec (where V_ξξ is the second derivative of the electrostatic potential along the CD bond), C_H (2₁₁) — C_H (2₁₂) = 2.42±0.50 kc/sec, C_D (2₁₁) — C_D (2₁₂) = 0.25±0.10 kc/sec, C_H (2₁₁) = 0.2±1.0 kc/sec, C_D (2₁₁) = 0.13±0.20 kc/sec, and 〈1/r_HD³〉^—⅓ = 1.88±0.10 Å. The V_ξξ calculated from the deuteron quadrupole coupling constants are, for HDO: 1.56×10¹⁵ statvolt/cm²; for HDS: 0.76×10¹⁵ statvolt/cm²; and for CHDO: 0.83×10¹⁵ statvolt/cm².