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1.
Heterodyne frequency measurements were made on selected absorption features of carbonyl sulfide (OCS) near 26 THz (860 cm?1) and 51 THz (1700 cm?1). Frequency differences were measured between a tunable diode laser (TDL) locked to carbonyl sulfide absorption lines and either a stabilized 13CO2 laser or a CO laser which was referred to stabilized CO2 lasers. These measurements are combined with conventional TDL measurements and published microwave measurements to obtain new, more reliable molecular constants for OCS, O13CS, and OC34S. New frequency measurements are given for nine CO laser transitions between 1686 and 1726 cm?1. 相似文献
2.
Frequency measurements are given for the 0001-0000 and 0111-0110 bands of N2O from 1257 to 1340 cm?1. The measurements utilize heterodyne techniques by measuring small frequency differences between a tunable diode laser locked to the center of an N2O absorption line and harmonic combinations of frequencies of radiation from two CO2 Lamb-dip-stabilized lasers. The measurements are facilitated by the use of the CO laser as a transfer laser whose frequency is also measured. These measurements have been combined with other data to provide new band constants and frequency calibration tables for several band systems of N2O in the following regions; 1215 to 1340, 1816 to 1930, and 2135 to 2268 cm?1. A correction factor is also provided for existing calibration tables near 590 cm?1. 相似文献
3.
A very close coincidence between the P(1) transition of the 1-0 band of D79Br and a CO laser line has allowed the observation of a DBr laser Stark spectrum. The observed inverse Lamb dips resolve the Br hyperfine structure of the transition, and are used to determine the value of the dipole moment of DBr in the v = 1 state. A high-resolution Fourier transform spectrum of DBr in the region 1750 to 1900 cm?1 has also been recorded and accurately measured. These new data, together with the best previous microwave and infrared measurements, are used to determine molecular parameters for DBr, and also result in improved secondary wavenumber standards for the 5.5-μm region. 相似文献
4.
《Journal of Molecular Spectroscopy》1996,175(1):190-197
We present a series of sub-Doppler frequency measurements of carbonyl sulfide (OCS) rovibrational transitions covering the spectral region around 2050 cm−1(61 THz). The absolute experimental uncertainties are between 21 and 84 kHz (Δν/ν = 3–14 × 10−10). In our spectrometer, tunable microwave sidebands are added to CO-laser lines and are used to saturate OCS transitions at low absorber pressure. The CO laser, plus a fixed-frequency sideband, is stabilized to the center of the OCS Lamb-dip signal and the laser frequency is measured against combination frequencies of two saturation-stabilized CO2lasers. The determined OCS transition frequencies are combined with other data in a least-squares fit. These measurements improve the accuracy of several carbonyl sulfide bands for calibration purposes by one to two orders of magnitude. New molecular constants and detailed calibration tables between 860 and 3100 cm−1are given. 相似文献
5.
Laser magnetic resonance spectra of the ν2 band of the NH2 radical have been observed with a CO2 laser in the 1030–1108-cm?1 range. The measurements of these weak ΔN = ?1, ΔKa = ?3 transitions, involving levels with 5 ≤ N ≤ 10, should complement measurements in the higher frequency half of the band (1500–1900 cm?1) made using CO lasers. 相似文献
6.
The v = 0?0 quadrupole spectrum of H2 has been recorded using a 0.005-cm?1 resolution Fourier transform spectrometer. The rotational lines S(1) through S(5) are observable in the spectra, in the region 587 to 1447 cm?1. The spectral position for S(0) was also obtained from its v = 1-0 ground-state combination difference. The high accuracy of the H2 measurements has permitted a determination of four rotational constants. These are (in cm?1) B0 = 59.33455(6); D0 = 0.045682(4); H0 = 4.854(12) × 10?5; L0 = ?5.41(12) × 10?8. The hydrogen line positions will facilitate studies of structure and dynamics in astrophysical objects exhibiting infrared H2 spectra. The absolute accuracy of frequency calibration over wide spectral ranges was verified using 10-μm CO2 and 3.39-μm CH4 laser frequencies. Standard frequencies for 5-μm CO were found to be high by 12 MHz (3.9 × 10?4 cm?1). 相似文献
7.
A. G. Maki J. S. Wells A. Hinz 《International Journal of Infrared and Millimeter Waves》1986,7(6):909-917
Heterodyne frequency measurements have been made on the 12°0-00°0 band of carbonyl sulfide in the wavenumber range from 1866 to 1915 cm–1. Frequency measurement techniques reported earlier are used to measure the OCS absorption lines by means of a tunable diode laser, a CO laser local oscillator, and two CO2 lasers used as secondary frequency standards. A table of calculated absorption frequencies is given for OCS from 1866 to 1919 cm–1. 相似文献
8.
From the observation of double resonance effects on the microwave spectrum two coincidences between 9.4 μm CO2 laser lines and infrared transitions of the ν6 → (ν6 + ν1) band of CF379Br have been determined: R(30) laser line coincident with qR2(7), F = 17/2→17/2 transition, R(28) laser line coincident with all four ΔF = 0 hyperfine components of the qQ8(13) transition. In both cases other infrared transitions lay within the tuning range of the laser. The frequencies of these two laser lines allowed calculations of the band center frequency ν0 = 1083.530 ± 0.001cm?1 and αA = 11.93 ± 0.3MHz, for the ν6 → (ν6 + ν1) band.αB constants were determined for the vibrational states v6, (v6 + v1), v1, and v3. 相似文献
9.
A.S. Pine 《Journal of Molecular Spectroscopy》1975,54(1):132-143
The tetrahedral splittings in the P and R branches of the ν3 band of natural methane have been examined with Doppler-limited resolution using a difference-frequency spectrometer. The spectra obtained by this difference-frequency mixer are compared to recent high-resolution grating spectrometer studies of 12CH4 and enriched 13CH4. The resolution, selectivity and precision are improved over the conventional methods. The mixing spectrometer utilizes tunable, narrow linewidth infrared radiation generated in the nonlinear optical crystal, LiNbO3 as the beat frequency between a CW argon ion and a tunable dye laser. This spectrometer covers the 2.2 to 4.2 μm infrared spectrum with an instrumental resolution of 5 × 10?4 cm?1 and continuous scans up to ~1 cm?1 and with ir power ~1 μW. 相似文献
10.
V. L. Kasyutich A. McMahon T. Barnhart P. A. Martin 《Applied physics. B, Lasers and optics》2008,93(2-3):701-711
We demonstrate what is, to our knowledge, the first use of mid-infrared laser absorption spectroscopy for trace-gas measurements of cyclotron target outputs used for the generation of radioactive carbon-11 in positron emission tomography (PET). The spectrometer was based upon a liquid-nitrogen-cooled lead salt diode laser generating single-mode radiation in the wavenumber range of 2230–2240 cm?1. The sample flowed to a multiple-pass optical cell with a total path length of 15.23 m and the laser radiation was detected by two liquid-nitrogen-cooled InSb photodetectors. We present the results of CO, N2O and CO2 measurements on PET trace cyclotron output and discuss future work on 11CO and 11CO2 detection. 相似文献
11.
J. P. Sattler T. L. Worchesky A. G. Maki W. J. Lafferty 《Journal of Molecular Spectroscopy》1981,90(2)
Heterodyne techniques have been used to measure the frequency differences between carbonyl sulfide (OCS) absorption lines and CO2 laser transitions. A tunable diode laser was used both to scan the OCS absorption spectrum and to provide a beat signal against a CO2 laser. Frequency differences as great as 8.6 GHz were measured. Many different OCS hot-band transitions were measured near 1050 cm−1, and the measurements on the 0200-0000 band have been extended to such high J levels (J′ = 86) that higher-order centrifugal distortion terms are needed to fit the data. 相似文献
12.
Robin S. McDowell Melvin I. Buchwald Michael S. Sorem Alan G. Robiette Catherine M. Deeley Welf A. Kreiner 《Journal of Molecular Spectroscopy》1985,112(2):363-376
A Fourier transform infrared spectrum of 91% 13CD4 has been recorded between 885 and 1193 cm?1 with a resolution of 0.04 cm?1. The frequencies of 600 lines were measured with an accuracy of ±0.003 cm?1. Of these, approximately 368 are assigned as allowed transitions in ν4, 95 are forbidden ν4 transitions, and 137 belong to ν2; maximum upper state J values are 20 for ν4 and 19 for ν2. The ground state tensor constants Dt, H4t, and H6t were obtained by fitting them to four rotational transitions observed by Kreiner and Opferkuch in the infrared-microwave double-resonance spectrum. An interacting-band analysis of the diad then yields 22 spectroscopic constants for these Coriolis-coupled fundamentals and fits the experimental frequencies with an rms deviation of 0.0055 cm?1 for 432 unblended lines that were assigned unit weight. A ν4P+(12) transition at 943.3812 cm?1, nearly coincident with the 10P(22) emission of the 12C16O2 laser, has been investigated by heterodyne spectroscopy and its detuning (?64 MHz) and absorption coefficient have been determined. Such coincidences may lead to the development of laser analytical techniques for 13CD4, which is a useful nonradioactive atmospheric tracer. 13CD4 transitions that are within 300 MHz of isotopic CO2 laser lines are tabulated for this purpose and for use in double-resonance experiments. 相似文献
13.
The adsorption of CO on Ni(111) has been studied using infrared reflection-absorption spectroscopy combined with LEED, Auger electron spectroscopy, thermal desorption spectroscopy and work function measurements. At low CO coverage (θ = 0.05) CO adsorbs on threefold sites with a strecthing frequency given by ωCO = 1817 cm?1. At θ = 0.30 all molecules have shifted to two-fold sites, and θ = 0.50, where a c(4 × 2) structure is observed, ωCO = 1910 cm?1. At θ = 0.57, with a (√7/2) × √7/2)R19.1° structure, one quarter of the molecules are adsorbed on top of the nickel atoms with the others in two-fold sites. Molecules bonded on the top sites give rise to a band at 2045 cm?1. The frequency shift due to dipole-dipole interactions is small compared with the shift resulting from bonding to different crystallographic sites. 相似文献
14.
The vibration-rotation spectrum of the ν9 band of C2H5Cl was recorded using a Nicolet 7199 Fourier Transform Infrared Spectrometer; the Q-branch, R(5)-R(6) multiplets, and P(21)-P(22) multiplets were investigated using a tunable semiconductor diode laser spectrometer. Constants derived from these assignments are (cm?1) ν9 = 973.8379(2), A9 = 1.039516(3), B9 = 0.183081(7), C9 = 0.164505(8). The line which coincides with the CO2 laser 10R(6), which has been employed in multiphoton dissociation studies, is tentatively assigned to the 203 18-213 19 transition. In addition, a very strong coincidence of transitions 199 11-199 10 and 199 10-199 11 with the CO2 10R(16) line is found, which can provide a good candidate for laser chemistry and infrared double resonance spectroscopy. 相似文献
15.
A.S. Pine 《Journal of Molecular Spectroscopy》1978,70(2):167-178
The Doppler-limited spectrum of H2CO in the 2700 to 3000 cm?1 region has been recorded using a tunable difference-frequency laser system. This region encompasses the ν1 and ν5 fundamental CH stretching bands of formaldehyde as well as a number of strongly interacting combination bands. The tunable laser spectrometer affords complete spectral coverage with a calibration precision better than 10?3 cm?1 for the transition frequencies and with absolute absorption intensity measurements better than 2%. The band centers for the ν1 and ν5 vibrations are measured to be 2782.4572 ± 0.0010 cm?1 and 2843.3254 ± 0.0015 cm?1 respectively, independent of the upper-state rotational constants. 相似文献
16.
Robin S. McDowell Martin J. Reisfeld Norris G. Nereson Burton J. Krohn Chris W. Patterson 《Journal of Molecular Spectroscopy》1985,113(1):243-249
The ν1 + ν3 band of 238UF6 has been observed at Doppler-limited resolution between 1291.5 and 1297.2 cm?1 in a statically cooled longpath cell at 226 K. The frequencies of 21 transitions belonging to P(22, 28, 30), 14 belonging to R(12, 30, 31), and 28 belonging to the Q branch with 41 ≤ J ≤ 71, were measured with an accuracy of ±0.002 cm?1. In addition, 53 frequency differences were measured in the Q branch between lines having different J assignments from Q(14) to Q(76). Five spectroscopic constants were fitted to these 116 data points with a standard deviation of 0.0006 cm?1. The rotational constants have nearly the values expected from a consideration of ν1 and ν3 themselves, and there is little evidence for interaction of ν1 + ν3 with other levels. 相似文献
17.
T. George S. Saupe M. H. Wappelhorst W. Urban 《Applied physics. B, Lasers and optics》1994,59(2):159-166
We present a very high-resolution heterodyne spectrometer based on a CO laser which operates down to fundamental-band transitions of the molecule. This allows us to detect saturated absorption signals on these transitions at very low pressure (0.4 Pa) and laser intensity (< 1 mW/cm2), yielding a linewidth of about 250 kHz. With the CO fundamental-band laser stabilized to these saturation signals we have measured the transition frequencies of the fundamental bands of three isotopic species to an accuracy of typically 20 kHz (v/v 3 × 10–10), referenced to the CO2 frequency standard. Together with additional frequency measurements of the first hot bands, these provide the first heterodyne frequency data of sub-Doppler accuracy for transitions in low lying bands of CO. They now represent the most accurate secondary frequency standard in the spectral region around 5 µm (60 THz). 相似文献
18.
The infrared spectrum of the ν2 band of nitric acid (HNO3) has been measured with a tunable diode laser in the frequency interval from 1690 to 1727 cm?1. A total of 430 assigned transitions have been analyzed to yield a set of nine rovibrational constants for the upper state with a standard deviation of 0.0012 cm?1. The band is primarily B type with a band center at 1709.568 ± 0.005 cm?1. Because of the absence of perturbations, the band constants can be used to calculate transition frequencies and relative intensities with a high degree of accuracy. 相似文献
19.
Kuniaki Nakagawa Toru Nakagawa Yoshifumi Ueda Kozo Kuchitsu 《Journal of Molecular Spectroscopy》1976,63(3):547-552
Laser Stark spectra of carbonyl sulfide have been measured with parallel and perpendicular polarization of a 9.4 μm band CO2 laser with the Stark field up to 90 kV/cm. Components of the P(2) and R(1) transitions of the 0310–0110 band and those of the P(1) transition of the 0400–0200 band for 16O12C32S have been analyzed. Band origins, 1052.9446 (4) cm?1 for 0310–0110 and 1057.7860 (5) cm?1 for 0400–0200, and dipole moments, 0.7035 (16) D for 0110 and 0.6810 (24) D for 031P, are obtained. 相似文献
20.
We present Doppler resolution limited spectra of the P(J) and R(J) multiplets for J ≦ 10 of the 10-μm CO stretch band of 12CD316OH using a tunable diode laser. Relative frequencies within the multiplets accurate to ±0.0002–0.0005 cm?1 are obtained, but no absolute frequencies are given. We are able to assign most of the hindered rotation and K substructure in these multiplets. The assignments are based on analyses of Stark-difference spectra combined with the ground-state microwave data and the intensity variations which are expected theoretically. The ground and excited state A, K = 1 asymmetry splitting parameters are measured to be δ1″ = (8.5450 ± 0.0080) × 10?3cm?1 and δ1′ = (9.7706 ± 0.0080) × 10?3cm?1, respectively. The ground-state value agrees well with the microwave results. A rapid-scan system for recording data and a computer-aided technique for calibrating and plotting the spectra are described. 相似文献