W. Klemperer

Determination of the structure of ArCO2 by radio frequency and microwave spectroscopy

The species ArCO2 produced by adiabatic expansion is structurally characterized by molecular beam electric resonance spectroscopy. ArCO2 is shown to have C2v symmetry. The spectroscopic constants obtained are: The derived structural constants for ArCO2 are: Comparison is made with a number of proposed Ar–CO2 intermolecular potentials. The determined force constants are shown to be poorly fitted by a spherical argon–oxygen interaction.

Radio‐Frequency Spectrum of Phosphine (PH3)

The electric resonance spectrum of phosphine (PH3) was measured at zero electric field for three rotational states, J=4, 5, and 7 with K=3. In addition, the J=K=2 and J=K=1 spectra were observed at several values for the electric field. The dipole moment (debye) is 0.57395±0.0003. The magnetic hyperfine constants (kilohertz) are cα=−114.90±0.13, cβ=−116.38±0.32 for the spin—rotation interaction of the 31P nucleus, and ζ α=8.01±0.08,ζβ=7.67±0.19 for the spin—rotation interaction of the 1H nuclei. The α constant is the mean interaction in the x and y directions, and the β constant is the interaction about the molecular z axis. No inversion doubling was observed (Δ〈1 kHz). The K=3 levels have K‐doubling fine structure as predicted by Nielson and Dennison, but the magnitude does not agree with their formula.

Spectroscopic Constants and Vibrational Assignment for the B3Π0u + State of Iodine

Portions of the iodine B 3Π0u+←X 1Σg+ absorption spectrum have been remeasured under high resolution. A new analysis of 719 lines in the 3–6, 4–7, 5–4, 7–5, 11–1, 12–2, 13–2, 25–0, and 29–0 bands, combined with previous measurements by Mecke, Loomis, and Brown, gives the following revised constants: ωe′=125.273u2009cm−1Te′=15770.59γe′=−4.0×10−7ωexe′=0.7016Be′=0.028969δe′=−3.5×10−8ωeye′=−0.00567re′=3.0276u2009ADe′=3.5×10−9ωeze′=+0.000032αe′=0.0001562βe′=3.9×10−10De′=4391.0 Constants for ground state rotational levels were found to be in good agreement with Ranks latest determinations.Using these new constants for the B state, Franck—Condon factors for this system were computed. The vibrational numbering originally assigned by Mecke and Loomis to the B state was decreased by one unit to bring calculated intensity distribution into complete agreement with all observed fluorescence data, including new photoelectric measurements on a number of bands. No systematic variation of the electronic transition moment could b...

Hyperfine Structure and Dipole Moment of CH3D

The electric resonance spectrum of deuteromethane (CH3D) was measured in the two rotational states, Ju2009=u20091, Ku2009=u20091 and Ju2009=u20092, Ku2009=u20092. From these data the dipole moment and hyperfine constants of the molecule were obtained. The results for the methane‐related spin rotation constants are cαu2009=u200916.54u2009±u20090.35, and cβu2009=u2009−u20091.58u2009±u20091.0 kHz. The quadrupole coupling constant eqQ at the deuterium nucleus is found to be eqQu2009=u2009191.48u2009±u20090.77 kHz. The electric dipole moments μ(J, K) are μ(1, 1)u2009=u20095.6409u2009×u200910−3 and μ(2, 2)u2009=u20095.6794u2009×u200910−3D.

Water hydrogen bonding: The structure of the water–carbon monoxide complex

Rotational transitions between J≤3 levels within the K=0 manifold have been observed for H2O–CO, HDO–CO, D2O–CO, H2O–13CO, HDO–13CO, and H217O–CO using the molecular beam electric resonance and Fourier transform microwave absorption techniques. ΔMJ=0→1 transitions within the J=1 level were also measured at high electric fields. A tunneling motion which exchanges the equivalent hydrogens gives rise to two states in the H2O and D2O complexes. The spectroscopic parameters for H2O–CO in the spatially symmetric tunneling state are [∼(B0) =2749.130(2)MHz, D0=20.9(2)kHz, and μa=1.055u200932(2)D] and in the spatially antisymmetric state are [∼(B0) =2750.508(1)MHz, D0=20.5(1)kHz, and μa=1.033u200907(1)D]. Hyperfine structure is resolved for all isotopes. The equilibrium structure of the complex has the heavy atoms approximately collinear. The water is hydrogen bonded to the carbon of CO; however the bond is nonlinear. At equilibrium, the O–H bond of water makes an angle of 11.5° with the a axis of the complex; the C2v axi...

Electric Dipole Moment of SiO and GeO

The molecular beam electric resonance spectra of SiO and GeO have been measured. The electric dipole moments (in Debye) of SiO and GeO in the lower vibrational states are: V28SiO74GeO03.09823.282413.11783.303223.13723.323933.1574 The difference between observed and calculated dipole moment is quite similar in CO and SiO.

Electric Dipole Moment of the 1A2 Electronic State of Formaldehyde

The measurement of the Stark effect of the near‐ultraviolet absorption spectrum of formaldehyde vapor is described. The magnitude of the electric dipole moment of the 1A2 (nπ*) state is 1.56±0.07 D and its direction is the same as that of the ground‐state dipole moment. The decrease of dipole moment on excitation (0.78 D) is much smaller than predicted from a naive molecular orbital model, but is in good agreement with the value (0.66 D) corresponding to the previously calculated orbitals of Foster and Boys.

Energy Transfer in the Fluorescence of Iodine Excited by the Sodium D Lines

Absorption of the sodium D lines excites I2 molecules predominantly to the vibration—rotation levels v′=14, J′=113; v′=15, J′=44 and 37; and v′=16, J′=106 of the B3II0+u electronic state. In the absence of foreign gases, approximately 75% of the excited molecules are in v′=15, 10% in v′=14, and 10% in v′=16. Steady‐state fluorescence from these levels and neighboring levels populated by collisions with added inert molecules has been used to obtain collision cross sections for exchange of vibrational energy of excited I2 with the translational energy of the gases He, Ne, Ar, Kr, Xe, H2, HD, D2, N2, O2, and NO. Relative emission intensities were measured photoelectrically. Vibrational transfer is highly efficient; cross sections for one quantum transfer average about ⅛ kinetic‐theory cross sections taken from gas viscosities and are similar to those obtained by other workers for transfer from v′=25. Information on multiple quanta transfer could not be obtained directly because of band overlapping. On transf...

The high‐resolution visible overtone spectrum of CH4 and CD3H at 77 K

We have obtained visible overtone spectra with Doppler‐limited resolution of methane and trideuteromethane in the vicinity of six quanta of C–H stretch. At room temperature, the methane spectrum is unresolved. Upon cooling to 77 K in a specially designed photoacoustic cell, methane shows a complicated but rotationally resolved spectrum. The widths of all features in the spectrum are consistent with Doppler broadened linewidths at 77 K. Efforts to assign this spectrum are in progress. The overtone spectrum of CD3H has been recently studied by other workers at a resolution of 0.5 cm−1 [Perry, Moll, Kupperman, and Zewail (preprint)]. The spectrum in this region consists of two parallel bands, one at 16u2009156 cm−1 and another at 16u2009230 cm−1. These are assigned as arising from a Fermi resonance between the pure C–H overtone 6ν1 and a combination with the degenerate C–H bend, 5ν1+2ν5. A high resolution spectrum taken at 77 K shows nearly completely resolved K‐subband structure for both bands. The rotational const...

Electric Resonance Spectroscopy of Hypersonic Molecular Beams

A hypersonic nozzle beam (Mach 19) of HCN molecules was studied by electric resonance spectroscopy. Translational temperatures of 4°K and rotational temperatures of 64± 30°K were found from a 283°K nozzle source. The monoenergetic character of the beam and the rotational cooling lead to an order of magnitude increase in signal‐to‐noise ratios. The absence of an appreciable velocity dispersion and a homogeneous radiation field allowed a critical comparison with theoretical two‐level resonance lineshapes. An SF6 diluent was used to reduce the beam velocity by one‐half and increase spectral resolution over a thermal (effusive) source. SF6 vibrational relaxation was observed. Chemically interesting species can be formed: ArXe, XeHCl, (HCl)2, (HCN)x, and (HF)x.