Far-infrared Laser Magnetic Resonance Spectroscopy Research Articles

The bending vibration of FeD2 at 226 cm−1, detected by far-infrared laser magnetic resonance spectroscopy

We report the first gas phase observation of a bending vibration in an open shell molecule by far-infrared laser magnetic resonance. The spectrum is due to FeD2; its observation shows that rovibrational transitions can be detected with such a spectrometer. The molecule was produced in the reaction between deuterium atoms and iron pentacarbonyl. FeD2 has a linear 5Δ ground state and shows the effects of Renner–Teller coupling in the excited vibrational (010) level.

Far-Infrared Laser Magnetic Resonance Spectroscopy of Vibrationally Excited CF Radicals

Pure rotational spectra of CF in the ν = 1 level of both 2Π3/2 and 2Π1/2 components of the ground electronic state have been observed by far-infrared laser magnetic resonance (FIR LMR) spectroscopy at 11 wavelengths between 337 and 1011 μm. These spectra have been analyzed and subjected to a global least-squares fit with all previous measurements relevant to the ν = 1 level, to obtain the vibrational dependence of all the major parameters. Several ν = 1 parameters have been determined for the first time. A small but significant vibrational dependence has been detected in two of the 19F hyperfine parameters.

Far-Infrared Laser Magnetic Resonance of X̃2A′ trans-DOCO

Far-infrared laser magnetic resonance spectroscopy is used to measure components of 12 rotational transitions in the deuterated hydroxyformyl radical. Ten different FIR laser lines are employed at wavelengths between 339 and 663 μm. The assigned transitions are all b-dipole in character. The new data complement the previously reported a-dipole spectrum [Radford et al., J. Chem. Phys.97, 3989-3995 (1992)] recorded in the millimeter-wave region. All of the existing high-resolution rotational spectra are subjected to a least-squares fit to the parameters appearing in the effective Hamiltonian describing the ground state of DOCO. The resulting parameters reproduce the existing spectroscopic observations to within the experimental accuracy and will be useful for predicting new spectra. The strongest resonances are well suited for future kinetics investigations of the radical.

Laser magnetic-resonance measurement of the 3P1-3P2 fine-structure splittings in 17O and 18O.

The 3 P 1 - 3 P 2 fine-structure splittings of 17 O and 18 O have been measured by far-infrared laser magnetic-resonance spectroscopy. The signals for 17 O were detected with a sample in its natural abundance (0.038%). The isotopic shifts from the corresponding interval in 16 O are +13.0 MHz for 17 O and +23.5 MHz for 18 O, in accord with theoretical expectations

Molecular parameters of chromium hydride in its X6Σ + state determined by far-infrared laser magnetic resonance spectroscopy

The far-infrared laser magnetic resonance spectrum of the CrH radical in the v = 0 level of its X 6Σ + state has been studied in detail. Signals associated with the five lowest rotational transitions have been detected. Nearly 500 resonances for 52CrH have been assigned and used to determine molecular parameters which describe the rotational energy, the fine and proton hyperfine splittings, and the Zeeman effect. These parameters are well determined and their implications for the structure of CrH are discussed. A fourth-order correction to the spin-spin coupling has been identified for the first time. Precise zero-field rotational transition frequencies have been calculated which may allow the detection of the CrH radical in the interstellar medium.

Rotational spectroscopy of DO2 by FIR LMR and millimeter-wave absorption

Abstract We report the measurement of approximately 50 rotational transitions in the DO 2 radical between 230 and 2530 GHz by high-resolution millimeter-wave and far-infrared laser magnetic resonance spectroscopy. The radical was generated in the gas phase by the reaction of chlorine atoms and oxygen or discharged oxygen with deuterated methanol. The data were analyzed in conjunction with previously published high-resolution spectra of the molecule in the ground vibronic state in order to extract the best set of parameters in the effective Hamiltonian describing the molecule. The fine structure (spin-rotation) parameters derived in the present work were used together with those for HO 2 [A. Charo and F. C. De Lucia, J. Mol. Spectrosc. 94, 426–436 (1982)] in order to determine all of the symmetry-allowed spin-rotation tensor components for the hydroperoxyl radical. The results cannot be interpreted in terms of contamination of the ground state wavefunction by the lowest lying A 2 A state alone and information from quantum chemical calculations of spin-orbit matrix elements between the ground and higher excited states or additional experimental data involving higher excited electronic states are necessary before a complete rationalization of the results is possible.

Precise measurement of the J=2←1 fine structure interval in N(II) by far-infrared laser magnetic resonance

Far-infrared laser magnetic resonance spectroscopy has been used to measure the J=2←1 fine structure intervals in the 3P ground states of singly ionized 14N and 15N atoms. In 14N(II) this separation is 2459.3703(14) GHz, and in 15N(II) it is 2459.3816(19) GHz. The hyperfine constants and gJ factors have been evaluated for both isotopes. Zero field energies for the hyperfine components of the J=2←1 transition in both isotopes are given in an effort to facilitate their observation in interstellar sources. A complete description of the hyperfine and Zeeman Hamiltonian matrix elements for atomic fine structure transitions is given in an LS coupled basis set.

Infrared and far-infrared laser magnetic resonance spectroscopy of the GeH radical: Determination of ground state parameters

The GeH radical has been detected in its ground 2Π state in the gas phase reaction of fluorine atoms with GeH4 by laser magnetic resonance techniques. Rotational transitions within both 2Π1/2 and 2Π3/2 manifolds have been observed at far-infrared wavelengths and rotational transitions between the two fine structure components have been detected at infrared wavelengths (10 μm). Signals have been observed for all five naturally occurring isotopes of germanium. Nuclear hyperfine structure for 1H and 73Ge has also been observed. The data for the dominant isotope (74GeH) have been fitted to within experimental error by an effective Hamiltonian to give a set of molecular parameters for the X 2Π state which is very nearly complete. In addition, the dipole moment of GeH in its ground state has been estimated from the relative intensities of electric and magnetic dipole transitions in the 10 μm spectrum to be 1.24(±0.10) D.

Far-infrared laser magnetic resonance of vibrationally excited CD_2

The detection of 13 rotational transitions in the first excited bending state (010) of CD2 using the technique of far-infrared laser magnetic resonance spectroscopy is reported. Molecular parameters for this state are determined from these new data together with existing infrared observations of the v(2) band. Additional information on the ground vibrational state (000) is also provided by the observation of a new rotational transition, and this is combined with existing data to provide a refined set of molecular parameters for the CD2 ground state. One spectrum has been observed that is assigned as a rotational transition within the first excited symmetric stretching state (100) of CD2. These data will be of use in refining the structure and the potential function of the methylene radical.

The rotational spectrum and hyperfine structure of the methylene radical CH2 studied by far-infrared laser magnetic resonance spectroscopy

Thirteen pure rotational transitions of CH2 in its X̃ 3B1 ground vibronic state have been measured and assigned using the technique of far-infrared laser magnetic resonance (LMR) spectroscopy. The energy levels thus determined led to the prediction and subsequent detection by microwave spectroscopy of a further rotational transition 404–313, at lower frequency (∼70 GHz). The analysis of these observations yields precise rotational constants as well as spin–spin, spin-rotation, and hyperfine interaction parameters for gas phase CH2. Its rotational spectrum may enable interstellar CH2 to be detected by radio astronomy. Two rotaional transitions within the v1=1 excited vibrational state have also been identified in the LMR spectrum. Future observations of vibrationally excited CH2 may afford a means of determining the singlet–triplet splitting in methylene, and studies of CD2 and CHD will result in improved structural determinations.