Submillimeter wave spectrum of methylene chloride, ¹²CH₂³⁵Cl₂, ¹²CH₂³⁵Cl³⁷Cl and ¹²CH₂³⁷Cl₂ up to 1.1 THz

High resolution spectra of methylene chloride in natural abundance are recorded in wide spectral regions from 0.075 up to 1.090 THz. The 5095 multiplet center frequencies with the value of quantum number J(max) = 107 and K-a(max) = 20 were assigned to the (CH2Cl2)-C-12-Cl-35 species. A weighed fit of the experimental data allowed us to obtain a set of 20 rotational and centrifugal distortion parameters which reproduce the initial experimental data with the d(rms) = 19 kHz in the whole region. Comparison with the literature values from microwave and from far infrared measurements is made. An analogous analysis was carried out for the (CH2)-C-12 (ClCl)-Cl-35-Cl-37 and (CH2Cl2)-C-12-Cl-37 species for which 4561 and 2465 transitions with J(max) = 100, K-a(max) = 19 and J(max) = 88, K-a(max) = 19 where assigned and analyzed. Sets of 20 fitted effective Hamiltonian parameters of (CH2ClCl)-C-12-Cl-35-Cl-37 and 15 fitted parameters of (CH2Cl2)-C-12-Cl-37 reproduce the assigned experimental transitions of the latter two isotopologues with the d(rms) = 20 kHz and d(rms) = 19 kHz, respectively and considerably improve the calculated line positions up to 1.1 THz in comparison with previous parameters.