Chi Matsumura

Microwave spectra of nitrogen trifluoride in the excited vibrational states: Equilibrium structure

Abstract The microwave spectra of two isotopic species of the NF3 molecule were investigated in the excited vibrational states. The vibration-rotation interaction constants α v B for the ν1, ν2, ν3 and ν4 states were found to be −43.45, +38.65, +78.81, and +4.48 MHz for 14NF3 and −38.41, +40.14, +75.67, and +4.64 MHz for 15NF3, respectively. The equilibrium rotational constant, Be, was then derived to be 10761.91 ± 0.2 MHz for 14NF3 and 10710.63 ± 0.2 MHz for 15NF3, from which the equilibrium structure was determined to be r e (N-F) = 1.365 ± 0.002 A and αe(∠FNF) = 102°22′ ± 2′. A set of linear relations was derived between cubic potential constants from the observed α v B and l-type doubling constants.

Structure of dichlorine monoxide as studied by microwave spectroscopy. Determination of equilibrium structure by a modified mass dependence method

Abstract The microwave spectra of four isotopic species of dichlorine monoxide (OCl2) have been observed, and the rotational constants have been obtained. The rm structure for each isotopic species has been determined by Watsons method. The equilibrium structure has been estimated by taking proper averages of rm structures to be r e (OCl) = 1.69587(7) A and ∠eClOCl = 110.886(6)°. The general applicability and the merit of the present method for estimating the equilibrium structure are pointed out.

The rotational spectra, molecular structure, dipole moment, and hyperfine constants of HOBr and DOBr

Abstract Pure rotational spectra of the 79Br and 81Br isotopic species of gaseous hypobromous acid, HOBr and DOBr, as well the v3 = 1 excited state of HOBr have been observed and analyzed. Structural parameters have been derived from the ground state rotational constants. The permanent molecular dipole moment of DOBr and the bromine nuclear quadrupole coupling and spin rotation constants of all the species have been determined.

Microwave spectrum of aminoborane, BH2NH2

Abstract The unstable species aminoborane, BH2NH2, has been identified as a reaction product of ammonia with diborane by microwave spectroscopy. The rotational constants determined are A = 138212 ± 4 MHz, B = 27487.83 ± 0.10 MHz and C = 22878.44 ± 0.11 MHz for 11BH2NH2 and A = 138199 ± 6 MHz, B = 28420.36 ± 0.11 MHz and C = 23520.78 ± 0.12 MHz for 10BH2NH2. The dipole moment is 1.844 ± 0.015 D.

Molecular structure of phosgene as studied by gas electron diffraction and microwave spectroscopy: The rs, rm, and re structures

Abstract The microwave spectra of eight isotopic species of COCl2 have been observed, and the following rotational constants have been obtained: An analysis of the rotational constants has resulted in the rs and rm structures. The equilibrium structure, re, has been estimated by combining the rm parameters derived according to Watsons method and the re bond distances estimated in our recent electron-diffraction and spectroscopic studies to be r e (CO ) = 1.1756 ± 0.0023 A , r e (CCl ) = 1.7381 ± 0.0019 A , ∠eClCCl = 111.79 ± 0.24°.

Microwave spectra of 13CH3 12CD3 and 12CH3 13CD3 and the C–C bond length of ethane

We observed the J=2←1, K=1 transitions of two doubly labeled ethanes 13CH3 12CD3 and 12CH3 13CD3, which were contained in natural abundance in a CH3CD3 sample. The measured frequencies were subsequently made more accurate using enriched samples. Assuming the centrifugal distortion constants DJ and DJK, which were determined for 12CH3 12CD3, we calculated the B0 constants to be 16 088.428±0.030 and 16 251.914±0.030 MHz for 13CH3 12CD3 and 12CH3 13CD3, respectively. By combining these with the B0 of 12CH3 12CD3(16 474.438±0.030 MHz), we derived the rs distance of C–C to be 1.526131±0.000083 A, where the error was due to uncertainties of the rotational constants. We also calculated the rz(C–C) distance to be 1.5312 A in 12CH3 12CD3 by transferring Kuchitsu’s rz(C–H), rz(C–D), ϑz(CCH), and ϑz(CCD). We evaluated the dipole moments of the two species from the Stark effects to be 0.01067±0.00010 D and 0.01094±0.00011 D for 13CH3 12CD3 and 12CH3 13CD3, respectively, which were to be compared with 0.01078±0.00009 ...

Microwave spectrum and molecular structure of gauche‐1,2‐difluoroethane

The microwave spectra of four isotopic species of gauche‐1,2‐difluoroethane have been observed. Having combined the rotational constants obtained with those of the normal species, all the structural parameters have been determined as follows; r(C–C)=1.493(8) A, r(C–F) =1.390(3) A, r(C–Hg)=1.099(2) A, r(C–Ht)=1.093(5) A, ∠CCF=110.6(5)°, ∠CCHg=108.4(6)°, ∠CCHt=111.3(6)°, ∠HCH=109.1(5)°, ∠FCHg=109.6(3)°, ∠FCHt=107.8(6)°, and FCCF (dihedral angle)=71.0(3)°. The spectra of normal species in the excited torsional states have also been observed up to vt=4, and the results of the analysis indicate that the gauche‐gauche barrier should be higher than the value, 468.6 cm−1, reported by the analysis of vibrational spectra.

Dipole moment of the HO2 radical from its microwave spectrum

Abstract Stark effects are measured for the 1 01 ← 0 00 , 7 17 ← 8 08 , and 9 09 → 8 18 transitions of the HO 2 free radical. The unresolved Stark patterns of the b -type transitions are analyzed by the use of computer simulation. Second-order perturbation theory, including the effect of spin-doublings in the denominators, is used for the calculation of the Stark effect coefficients. The dipole moment determined is μ a = 1.412 ± 0.033 D, μ b = 1.541 ± 0.016 D, and μ total = 2.090 ± 0.034 D.

Microwave spectrum of allene‐1, 1‐d2

The J = 3 ← 2, K−1 = 2 and J = 4 ← 3, K−1 = 2 and 3 transitions were observed for the allene‐1,1‐d2 molecule. The B = (B + C)/2 and (A−B)bp2 constants have been determined to be 7846.158 ± 0.01 MHz and 0.133 ± 0.005 MHz, respectively. The observed values of the two centrifugal distortion constants, DJ = 0.0024 ± 0.0005 MHz and DJK = 0.130 ± 0.005 MHz, were compared with the calculated to confirm the assignment of the weak spectra. The Stark effect of the J = 4 ← 3, K−1 = 3 transition was analyzed by comparing with computer‐simulated spectrum, leading to the dipole moment of 0.0031 ± 0.0003 D.

Microwave spectrum of acetonitrile-d3, CD3CN

Abstract The microwave spectrum for the J = 2 ← 1 transition of the CD 3 CN molecule was investigated. The molecular structure was determined from the observed spectra of CD 3 CN, C 13 D 3 CN, CD 3 C 13 N, and CD 3 CN 15 . A number of spectral lines of the molecule in the excited vibrational states, ν 8 , 2 ν 8 , 3 ν 8 , 4 ν 8 , 5 ν 8 , ν 7 , ν 6 , ν 4 , and ν 3 , were measured and analyzed. The observed l -type doublings and the splittings in highly excited states were well interpreted by the theory. An anomaly in the Stark pattern of the ν 7 excited lines was noticed and explained by the accidental near degeneracy of the ν 4 and ν 7 vibrations.