Laser Magnetic Resonance Spectra Research Articles

Re-investigation of the infrared spectrum of the NCN radical by laser magnetic resonance spectroscopy

The laser magnetic resonance (LMR) spectroscopic technique has been used to reinvestigate the mid-infrared spectrum of the NCN free radical in its Σg-3 ground electronic state. A liquid nitrogen-cooled carbon monoxide (CO) laser was used as a source of strong coherent radiation in the 1442–1484 cm−1 region of the infrared. Vibration-rotation transitions were brought into resonance with the laser frequency using magnetic flux densities up to 1.4 T. Spectra were recorded in both parallel (ΔMJ = 0) and perpendicular (ΔMJ = ±1) polarizations with ten CO laser lines. Over one hundred new absorption lines were observed in the LMR spectra and have been subsequently assigned to transitions in either the 301 fundamental band (near 1466.5 cm−1) or the 211301 hot band (near 1455.6 cm−1) of NCN in the Σg-3 ground state. An improved set of molecular parameters for NCN has been determined from a least-squares fit of all the available data on the infrared spectrum, provided by Fourier transform and LMR spectra. In the wake of an exhaustive analysis of the LMR spectra, several additional lines remain. Although chemical tests indicate these lines do not belong to NCN, it has not proved possible to identify their carrier(s).

Dependence of Zeeman splitting of spectral lines on the magnetic field magnitude for NO molecule

The paper presents an overview of experimental and theoretical results, which were obtained from the study of the dependence of Zeeman splitting of the vibrational-rotational lines of the 0–1 band of the nitric oxide molecule absorption spectra on the magnetic field magnitude. The experiments were performed at the Laboratory of Gas Lasers of P.N. Lebedev Physical Institute, Russian Academy of Sciences (FIAN). The method of laser magnetic resonance (LMR) with the use of a continuous-wave frequency-tunable CO laser were used to record the spectra. The theoretical analysis of LMR spectrograms was carried out at the Laboratory of Theoretical Spectroscopy of V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (IAO SB RAS), where the numerical model was developed based on construction of the total effective Hamiltonian of the molecule accounting the interaction with an external magnetic field. The model allows calculation of LMR spectra under given conditions and description of the nonlinear dependence of splitting of rovibrational energy levels on the magnetic field magnitude. The comparison of calculated and experimental LMR spectrograms has shown that the numerical model adequately reproduces the positions of absorption peaks measured in a damped oscillating magnetic field.

Laser magnetic resonance study of the ν2 bending of NO2 using a CO2 laser: Line positions and intensities

The ν2 rovibrational bands (010←000 and 020←010) of NO2 were studied using CO2 laser magnetic resonance (LMR). Thirty-six CO2-laser lines were used to record approximately 200 Zeeman resonances in the 886–982cm−1 range with perpendicular polarization (E⊥H). All resonances were assigned using molecular parameters from the literature. The intensities of the LMR spectra (both overlapping and not overlapping) were calculated, and the most intense spectra were assigned using the analysis. A new type of LMR signal, which was non-resonant, was observed and described.

Assignment of far-infrared laser magnetic resonance spectrum of CH 2Br radical at 447.3 and 672.1 μm

Assignment of far-infrared laser magnetic resonance spectrum of CH 2Br radical at 447.3 and 672.1 μm

Part of the far-infrared laser magnetic resonance spectrum of the HF + free radical

Transitions between the spin-rotational levels of the HF + radical in the v=0 level of the X 2Π ground state have been observed by the technique of laser magnetic resonance at far-infrared wavelengths. Because of the large spin–orbit coupling in this 2Π state, the detection of the fine-structure transitions required the use of very short-wavelength laser lines (down to 40 μm). These observations have provided accurate information on the 19F hyperfine splittings in rotational levels of the upper 2 Π 1/2 spin component for the first time which has enabled the complete determination of the hyperfine structure for this molecule. An effective Hamiltonian was used to model the experimental measurements; this provided considerably more accurate values for the various molecular parameters than previously available. Using these parameters, predictions of the transition frequencies between the low-lying spin-rotational levels of the radical at zero magnetic field have been made.

The far-infrared laser magnetic resonance spectrum of the 13CH radical

Transitions between the spin-rotational levels of the 13CH radical in the v=0 level of the X 2 Π ground state have been detected by the technique of laser magnetic resonance at far-infrared wavelengths. These measurements have been combined with the previous measurements of the lambda-doubling intervals of the molecule [J. Chem. Phys. 85 (1986) 1276 ] to determine an improved set of molecular parameters for 13CH. The analysis provides accurate predictions of the transition frequencies between the low-lying spin-rotational levels of the radical at zero magnetic field. A comparison is made with the values of the corresponding parameters of 12CH which reveals small effects due to the breakdown of the Born–Oppenheimer approximation.

Far-infrared detection of $^{\mathsf{17}}$OH towards Sagittarius B2

The frequencies and line strengths of the 2 Π3/2 J = 5/2-3/2 rotational transition of 17 OH have been calculated from an analysis of its far-infrared laser magnetic resonance spectrum. These results have been used to make the first detection of a pure rotational transition of 17 OH in the ISM. Two resolved components of this transition appear in absorption towards the giant molecular cloud Sagittarius B2, which was observed at a spectral resolution of 33 km s −1 with the Fabry-Perot mode of the ISO Long Wavelength Spectrometer. The corresponding transition of 18 OH was also observed and its line shape was modelled using H  measurements. The 18 O/ 17 O ratio of 3.5 was then used to compare this with the observed 17 OH line shape.

Studies of the mid- and far-infrared laser magnetic resonance spectra of the CD radical: information on vibrationally excited levels

Two separate studies of the CD radical in vibrationally excited levels of its X 2 Π ground state have been made by the technique of laser magnetic resonance. The first of these studies was in the far-infrared; rotational transitions of CD in the v = 1 and 2 levels have been detected. The second study was carried out in the mid-infrared using a carbon monoxide laser magnetic resonance spectrometer. In these experiments, transitions in the (1,0), (2,1), and (3,2) bands have been detected. All the available data on CD in its X 2 Π state have been used to determine an improved set of molecular parameters for the CD radical. In addition to the above data sets, previous far-infrared laser magnetic resonance on the CD radical in the v = 0 level and FTIR observations of the (1,0) and (2,1) bands have been included. The principal molecular parameters determined are: ν 0 = 2032.03360 ( 18 ) cm - 1 , ω e x e = 34.72785 ( 58 ) cm - 1 , B 0 = 7.7018632 ( 14 ) cm - 1 , α B = - α e = - 0.212239 ( 11 ) cm - 1 , where the figures given in parentheses are one standard deviation from the least squares fit. A small but significant dependence of the orbital contribution to the magnetic dipole moment on the vibrational quantum number is detected. This may reflect the mixing between the X 2 Π and a 4 Σ - states of CD.

Analysis of far-infrared laser magnetic resonance spectra of CH 2 Br at 447.3 and 671.1µm

A simple model has been developed to describe the Zeeman patterns of far-infrared laser magnetic resonance spectra of the monobromomethyl radical CH2Br observed at 447.3 and 671.1mum. A satisfactory agreement between the experimental spectra of the radical and their simulation with this simple model has been achieved. This approach can be used to gain further information about the structure and the spectrum of this interesting radical.

Far-infrared LMR spectroscopic investigation of the quasi-linear molecule DCCN: The v5(1 0) transition

The far-infrared laser magnetic resonance spectrum (FIR LMR) of the v5 bending vibrational transition of DCCN in its X3 Σ– state is reported. The DCCN radical was produced inside the spectrometer cavity by the reaction of deuterated acetonitrile with F atoms. DCCN resonances were measured on seven laser lines. Nitrogen hyperfine structure was observed on a number of the resonances. The analysis provides improved accuracy for the separation v5= 1 [Formula: see text] 0 and some of the 14N hyperfine coupling constants for this isotopomer.PACS No.: 33.20Ea

Laser magnetic resonance spectrum of the OD radical ( [formula omitted], v=0) at 118.6 μm

Far infrared laser magnetic resonance (FIR LMR) spectrum of OD ( 2Π 3/2 , v=0) has been observed. Data are presented for the Zeeman components of the rotational transition J=3.5→4.5 observed at 118.6 μm using a discharge water vapour laser spectrometer. Theoretical values of the transition magnetic field strengths have been calculated using the best available molecular constants. The agreement between theory and experiment confirms the spectroscopic assignments.

The Far-Infrared Laser Magnetic Resonance Spectrum of CH2F

Far-infrared laser magnetic resonance (FIR-LMR) spectra due to the CH2F radical have been recorded on seven laser lines at wavelengths between 301 and 568 μm. Observed resonances were assigned to fine and hyperfine components of pure rotational transitions of CH2F in the ground vibrational state and the first excited state of the ν4out-of-plane bending mode. All assigned transitions obeya-dipole selection rules. The data were combined with previously reported microwave results (Y. Endo, C. Yamada, S. Saito, and E. Hirota,J. Chem. Phys.79, 1605 (1983)) and subjected to a least-squares fit to determine the parameters of the effective Hamiltonian describing thev4= 0 and 1 vibrational levels of the CH2F radical.

CO LASER MAGNETIC RESONANCE SPECTRUM OF 15N16O AND ITS ANALYSIS WITH SPECTRA OF 15N17O AND 15N18O

Employing the intracavity absorption technique,Lamb dip of the spectrum was obtained and the resolution and sensitivity of CO Laser magnetic resonance(LMR) spectrometer was greatly improved. By this technique, the X2Π3/2(υ=1←0) Zeeman transitions of 15N16O were observed with the Λ-doubling and hyperfine structures resolved. A correlative analysis of the LMR Spectrum of 15N16O with the previous available measurements was performed. The global least-square fit provided by far the most complete and the most accurate molecular constants of all the related isotopic species of 15NmO(m=16—18). The accuracy of these constants is improved by 1 or 2 orders. Many of the molecular constants including γ, AD, Δ01, Δ10, Δ00 were determined for the first time.

Far Infrared Laser Magnetic Resonance Detection of CF3, CHF2, and CH2F

AbstractFar infrared laser magnetic resonance (FIR‐LMR) spectra of CF3, CHF2, and CH2F radicals were observed in the 300–800 μm wavelength region in the reactions of F atoms with a series of different hydrocarbon and partially fluorinated hydrocarbon molecules. To identify the carriers of the observed resonance patterns and to exclude or identify contamination of the spectra by additional resonances from other paramagnetic species, numerous chemical tests were developed and performed. With optimized sources and the chemical tests in hand, many spectra could be unambiguously attributed to CF3, CHF2, and CH2F, respectively. The present study reports the first gas phase detection of CHF2 radicals in their ground electronic state.

The ν3Band of the NCN Radical, Studied by LMR

The laser magnetic resonance (LMR) spectrum of NCN in its ground3Σ−gstate has been recorded for the first time, using a CO laser operating near the ν3vibrational band origin of NCN (∼1466.5 cm−1). As a result of small rotational and spin splittings, the LMR spectrum is very complex, particularly near the band origin. The LMR data have been fit in conjunction with very recent FTIR data, using some ground state parameters from a related study of the electronic spectrum performed in our laboratory, to yield accurate molecular parameters for NCN in its ground and excited vibrational states.

CO laser frequency stability determined by a laser magnetic resonance method

A method of CO laser frequency stability measurement is proposed, based on the molecular laser magnetic resonance (LMR) spectrum, which can be used to measure the linewidths of molecular LMR spectra and their changes. The data were treated by the Allan variance method. A series of CO laser frequency stability measurements were obtained from 0.1 s to 1000 s in the time domain. The frequency stability was fitted to a power law function. The expressions of frequency stability were found for a stabilized and a free-running CO laser in the frequency domain.

Laser Magnetic Resonance Measurement of the [TSUP]3[/TSUP][ITAL]P[/ITAL][TINF]1[/TINF]–[TSUP]3[/TSUP][ITAL]P[/ITAL][TINF]0[/TINF] Fine-Structure Separation of P[TSUP]+[/TSUP

The far-infrared laser magnetic resonance spectrum associated with the J = 1 ← 0 fine-structure transition of 31P+ in its ground 3P state has been recorded. This is the first laboratory observation of this magnetic dipole transition, and its frequency has been measured 2 orders of magnitude more accurately than the previous, indirect determination from optical spectroscopy. The frequency is ΔE10 = 4944433.0 ± 1.7 MHz. A small nuclear hyperfine splitting was also observed for the J = 1 level.

Detection of SO (X 3Σ −, v = 1) at 618.4 μm by laser magnetic resonance spectroscopy

Laser magnetic resonance (LMR) spectrum of 32S 16O in the X 3Σ − state has been observed in the far IR region at 618.4 μm with a vinyl bromide optically pumped laser as a source. Data are presented for the Zeeman components of the rotational transition N = 6, J = 7 → N = 7, J = 7 in the first vibrational excited level. Theoretical values of the transition magnetic field strengths have been calculated using the best available molecular constants and first order Zeeman formulas. The agreement between theory and experiment confirms the spectroscopic assignments.

Identification and Analysis of the Far-Infrared Laser Magnetic Resonance Spectrum of the HS 2 Radical

The first observation of the far-infrared laser magnetic resonance spectrum of the HS 2 radical in its ground 2 A″ state is reported. The radical was produced in the gas-phase reaction between fluorine atoms and hydrogen sulfide, H 2S. Spectra associated with several different rotational transitions (with values of N up to 30 and K a up to 4) have been identified and analyzed to give an improved set of molecular parameters. In particular, the value for the centrifugal distortion constant Δ K of 24.339(10) MHz is significantly different from the value assumed by S. Yamamoto and S. Saito ( Can. J. Phys. 72, 954 (1994)) in their earlier millimeter-wave study, Zeeman parameters have also been determined.

Frequency determination of far infrared optically pumped laser lines of vinyl fluoride using a niobium nitride Josephson mixer

Using the alternating current Josephson effect in a thin film niobium nitride (NbN) Josephson tunnel junction, we report the first accurate frequency measurements of optically pumped far infrared laser lines of vinyl fluoride (C2H3F). High harmonics of the local oscillator microwave source were mixed with the vinyl fluoride laser line in the junction and the intermediate frequency beat measured. The precise laser frequencies, and their CO2 pump lines are 902.001 593(42) GHz, 10P6; 889.341 248(67) GHz, 10P38; 673.997 567(19) GHz, 10R20; 634.221 681 (47) GHz, 10P20; 453.652 59(11) GHz, 10P24; and 446.698 886(30) GHz, 10P36. These frequencies are currently being used to analyse laser magnetic resonance spectra of the CF and CH2Br free radicals.