Method Of Laser Magnetic Resonance Research Articles

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.

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.

Line-broadening measurements of CH 2 ( [formula omitted]) rotational transitions by far-infrared laser magnetic resonance

Collisional line-broadening (pressure-broadening) measurements have been performed using the method of Laser Magnetic Resonance (LMR) for selected rotational transitions of CH 2 ( X ̃ 3B 1) in the far-infrared with 11 interesting bath gases ( M = He, Ne, Ar, Kr, N 2, SF 6, H 2, D 2, CH 4, C 2H 6, and H 2O) at room temperature. In addition, the temperature dependence has been studied for M = Ar, N 2, and CH 4. Neglecting contributions from elastic rotational dephasing or reorientation collisions, the results correspond to relaxation cross sections between σ = 16 A ̊ 2 for M = He to σ = 195 Å 2 for H 2O.

The time-resolved LMR method as used to measure elementary reaction rates of CI atoms and SiH 3 radicals in pulse photolysis of S 2Cl 2 in the presence of SiH 4

The time-resolved laser magnetic resonance (LMR) method has been applied to kinetic measurements for the first time. An intracavity spectrometer based on a CO 2 laser with resonant modulation of the magnetic field and with phase-sensitive detection of the signal has been used. Kinetic curves of generation and disappearance of CI atoms and SiH 3 radicals were obtained in the pulse photolysis of a mixture of S 2Cl 2 + SiH 4 under the fourth harmonic of a Nd laser (265 nm, 0.5 mJ, 12.5 Hz) at a total pressure of 520–980 Pa (he as diluent) and a temperature of 326 K. The reagent concentrations were: [S 2Cl 2 = (2.0−10.2)×10 14 cm −3, [SiH 4 = (2.4−17.4)×10 13 cm −3. To remove the transition saturation, 5.3×10 15 cm −3 CCl 4 was introduced into the reactor. The fraction of dissociated S 2Cl 2 was 1‰ Rate constants of the reactions (I) Cl+S 2Cl 2 → products, (II) Cl+SiH 4 → HCl+SiH 3 and a preliminary rate constant of the reaction (III) SiH 3 + S 2Cl 2 → products were obtained: k 1 ≤ (4.3±1.2)×10 −12 cm 3/s, k 2 = (2.3±0.5)×10 −10 cm 3/s, k 3 = (2.4±0.5)×10 −11 cm 3/s. At a signal-to-noise ratio of 1:1, 1000 pulses and a 12 cm long detection zone the sensitivity to Cl atoms and to SiH 3 radicals was 4×10 10 cm −3 and = 10 11 cm −3, respectively. The time resolution of the method was 4 μs. The method is shown to be promising for kinetic investigations and experiments on fast processes.

Analysis of the LMR spectra of methoxy, CH3O

The rotation spectrum of the free methoxy radical (CH3O) has been measured at 18 discrete wavelengths between 0.25 and 0.65 mm by the laser magnetic resonance method. A least-squares fit to the measured spectra yields precise values for the molecular parameters of the 2E ground state of CH3O.

Motional-Stark-effect spectroscopy:7S1−9P1energy separation and Zeeman tuning parameters forHe4

The 7 /sup 1/S-9 /sup 1/P energy separation of /sup 4/He has been measured by the method of laser magnetic resonance in electron-beam-excited /sup 4/He. The measurements have also provided Zeeman tuning coefficients for terms up to fourth order in the field B. Motional-Stark-effect (MSE) -dominated line shapes are observed at most fields. These line shapes are analyzed, and their Doppler-free portions used to obtain a value for the energy separation with a precision exceeding 1 ppm (..delta..E/sub 0/ = 980.7979 +- 0.0002 cm/sup -1/). Arguments are presented that show the importance of the MSE in magnetically confined hot plasmas and in certain collapsed stars possessing high magnetic fields.

High-resolution laser magnetic resonance and infrared-radiofrequency double-resonance spectroscopy of NO and its isotopes near 5.4 μm

The fundamental band of NO has been investigated by the laser magnetic resonance method, in which the absorption lines from an NO sample located inside the laser cavity were Zeeman tuned into resonance with fixed CO laser transitions. Saturation dips with a width of <2 MHz were observed, allowing the resolution of hyperfine and Λ-doubling structure in the NO spectrum. Transitions due to the weak 2-1 “hot” band and the 2 Π 1 2 ← 2 Π 1 2 satellite band of 14N 16O were observed, as were transitions due to the 15N 16O, 14N 18O, and 14N 17O isotopic species in natural abundance. Data from the present work were combined with previous measurements to obtain a consistent set of vibration-rotation parameters for five isotopic species of NO. An infrared-radiofrequency double-resonance spectrum was observed which allowed the precise (∼20 kHz) measurement of some hyperfine Λ-doubling transitions within the v = 1 state of 14N 16O.