R. S. Altman

The microwave spectrum and molecular structure of CO2–HCl

Radio frequency and microwave molecular beam electric resonance spectra have been obtained for three isotopic species of the hydrogen‐bonded weakly bound complex CO2–HCl. The following spectroscopic constants have been determined: This complex most likely has a linear equilibrium geometry with an O–H bond length of 2.14 A. A large induced dipole moment is found in this complex. A comparison of structural properties for this and other related weakly bound molecules is made.

Observation and analysis of the ν2 and ν3 fundamental bands of the H2D+ ion

The high‐resolution absorption spectrum of the D2H+ molecular ion in the 1800–2300 cm−1 region has been measured in a discharge through a mixture of H2 and D2 using a tunable infrared diode laser source and a cooled hollow‐cathode absorption cell. A total of 72 new lines of D2H+ have been observed, as well as five previously measured in ion‐beam experiments by Wing and Shy, and these have been assigned to specific rotational transitions of the ν2 and ν3 fundamental bands. Two different and complementary theoretical models are used to fit these data: one is an A‐reduced asymmetric rotor effective Hamiltonian including the Coriolis and higher‐order rotational interactions between ν2 and ν3; and the other is a supermatrix model in which the matrix of the untransformed Hamiltonian is set up and diagonalized directly, using a large vibration–rotation basis that diagonalizes the vibrational energy. The former approach is less expensive and provides a better fit, but because of the large number of parameters var...

The microwave spectrum and molecular structure of N2–HCl

The structure of the van der Waals molecule N2–HCl has been determined by molecular beam electric resonance spectroscopy. The microwave spectrum is well fitted by a linear hydrogen‐bonded structure with the following spectroscopic constants: Constant              14N2–H 35Cl   15,14N2–H35Cl   14,15N2–H35Cl In addition, spectra for the two chlorine isotopes of the complex formed using 15N2 are presented and analyzed. Electric quadrupole coupling hyperfine structure of 14N and 35,37Cl, is used to determine the vibrationally averaged orientation of the submolecules. The HCl submolecule makes an average angle of 26° with the a axis of the complex in all isotopes studied, while the average angle for the N2 submolecule is estimated to be 19°. The hydrogen–bond length is 2.42 A in the linear configuration which is virtually identical to the hydrogen‐bond length in OC–HCl. It is shown that the electric dipole moments of a series of N2 and CO complexes are not simply related to the polarizabiliti...

High resolution infrared spectroscopy of the ν1 (NH stretch) and ν2 (CH stretch) bands of HCNH

The infrared spectrum of the ν1‐band (NH stretch) and the ν2‐band (CH stretch) of protonated hydrogen cyanide HCNH+ has been observed based on recent theoretical predictions. This is the first observed spectrum of this ion in any wavelength region. From a least‐squares analysis of the rovibrational bands, the following spectroscopic constants have been obtained (in cm−1): ν1 (NH stretch) ν2 (CH stretch) ν0 3482.844 1(10) 3187.863 8(4) B1    1.228 633(39)    1.228 494(19) B0    1.236 024(37)    1.236 067(18) D1    1.574(43)×10−6    1.610(22)×10−6 D0    1.596(42)×10−6    1.620(21)×10−6 It is hoped that the rotational constants determined in this paper will lead to the identification of the microwave spectrum of this molecule in interstellar space.

Infrared spectra of 4HeH+, 4HeD+, 3HeH+, and 3HeD+

Isotopic species of the HeH+ molecular ion provide an excellent testing ground for studying isotopic dependence of vibration–rotation constants because of the small masses of He and H isotopes. We have observed infrared spectra of the hot band v=2←1 of HeH+ and fundamental bands of isotopic species HeD+, 3HeH+, and 3HeD+, and obtained the Dunham coefficients Ykl, and the isotopically independent parameters Ukl, ΔHekl, and ΔHkl.

The infrared spectrum of KH

Reported here is the first observation of the infrared spectrum of KH. Fundamental bands and first hotbands of the 39KH and 41KH isotopic forms were measured at high resolution using a diode laser based spectrometer. An ac glow discharge through potassium vapor and hydrogen gas was used to produce KH. A combined isotopic Dunham coefficient analysis was used to fit all the spectra, with the Dunham coefficients for 39KH coming out as Y10=985.6714(30) cm−1, Y20=−14.9013(10) cm−1, Y01=3.416 40(10) cm−1, Y11=−0.085 313(26) cm−1, Y21=5.41(60)×10−4 cm−1, Y02=−1.6354(36)×10−4 cm−1, Y12=1.13(10)×10−6 cm−1, Y03=7.6(8)×10−9 cm−1, (quoted at 2σ error limits). A bond length of 2.241 152(16) A and a Dunham corrected value for ωe of 986.0505(30) cm−1 are obtained. The pressure broadening of KH by H2 and the chemistry of KH formation in the glow discharge plasma are also discussed.