Search

Due to challenges in preparing pure metal clusters and in controlling reactions, the oxides produced by metal clusters reacting with oxygen are often different from traditional ion-molecule products in the gas phase and their reactivity pattern is also largely unveiled yet. In this work, utilizing a customized Re-TOFMS having a home-made cluster source and a flow tube reactor, we have observed the gaseous reactions of Nin± clusters with oxygen and found magic clusters of Ni13O8± that dominate the mass distributions. By quantum chemistry calculations, we find that both Ni13O8− and Ni13O8+ clusters bear a regular cubic structure with 8 oxygen anchoring the eight angles, however, they have rather different spin accommodations. The Ni13O8− clusters have 15 unpaired spin-up electrons exhibiting cubic aromaticity and decent ferromagnetism, while the Ni13O8+ clusters take a lower-spin ground state (11 unpaired electrons), with spin-down population on the central Ni atom pertaining to ferrimagnetism. This is a class of metalloxocube clusters that hold properties of aromaticity and ferromagnetism/ferrimagnetism charcterized by a few spin electrons, which embodies the bonding nature of superatomic compounds and enables to develop cluster-genetic materials of multi-functionality.

We report a joint experimental and theoretical study on the reactions of cobalt clusters (Con±/0) with nitrogen using the customized reflection time-of-flight mass spectrometer combined with a 177....

A novel nanosecond transient electric field (E-field) measurement system is developed in this paper to measure the E-field pulse caused by the operation of the high-voltage switch (switching E-field pulse) in the substation. An electrically small rod antenna is used as the receiving antenna and is matched by the operational amplifier with high input impedance to achieve broadband frequency response and stable working performance. A broadband analog optical fiber transmission system is further designed based on the high-frequency circuit model of the electronic components. Unlike the traditional frequency domain E-field measurement methods, the developed measurement system can directly output the time domain waveform of the switching E-field pulse. It also has the advantages of adjustable sensitivity, portability, and anti-electromagnetic interference. The calibrated measurement bandwidth ranges from 200 Hz to 680 MHz. Furthermore, the switching E-field pulse in an ultra-high voltage substation is measured and analyzed to verify the effectiveness of the fabricated measurement system.

Quantum statistics of identical nuclei in molecules gives rise to nuclear spin isomers. Except for methanol (CH3OH) that has internal rotation (i.e., torsion), all the studied molecules so far have overall rotational symmetry. Methanol does not rotate around the overall rotational symmetry axis but the methyl group axis. The identical nuclei in the methyl group produce a specific type of nuclear spin isomers of the ortho-CH3OH and para-CH3OH in methanol. Conversions between these two spin isomers have been observed in the experiment and a theory based on the rho-axis method (RAM) for partially explaining their conversions has been developed by us recently. However, besides RAM the internal axis method (IAM) is a classical method commonly used by many researchers and the coupling of the angular momenta between torsion and overall rotation in methanol can be completely separated from each other in the IAM. In this paper, as a series work we present a general theoretical model about conversion of ortho–para methanol using the IAM based on quantum relaxation theory. The expressions of the ortho–para state-mixing strengths induced by the nuclear spin–spin and nuclear spin–rotation interactions have been analytically deduced and numerically calculated. We found that the ortho–para states-mixings and ortho–para conversion can be induced by all these two intramolecular interactions whereas the nuclear spin–rotation interaction plays a major role. The conversion rate at temperature 300 K and pressure 1 Torr summed over eight ortho–para level pairs with gaps less than 2.7 GHz is calculated to be 1.4 × 10−2 s−1, which is close to the measured value of 2.1 (3) × 10−2 s−1, indicating the quantum relaxation is the leading process in the spin isomers conversions of methanol and suggesting our theory to be valid for other gaseous methanol-like molecules having torsion tunneling of symmetrical group. The most probable gateways in methanol for collision-induced population transfers are found to be levels-pairs in the ground-state A–E species of (υt J, K, p) = (0, 24, 4, 1)−(0, 25, 2, 1) by nuclear spin–spin coupling, (0, 22, 5, p)−(0, 21, 6, −1) and (3, 34, 1, 0)−(3, 35, 0, 1) by nuclear spin–rotation coupling.

A customized reflection time-of-flight (Re-TOF) mass spectrometer combined with a 177 nm deep-ultraviolet laser has enabled us to observe well-resolved cobalt clusters Con±/0 and perform a comprehe...

Reducing sizes of precious metals and utilization of the mixed small clusters of them as catalysts in reactions are important methods due to more active sites for higher catalytic efficiency. Based on first-principles calculations in this work, we found that the platinum-based clusters of Pt3X (X=Al, Si, Cu) which have the magic number 4 can effectively catalyze the water decomposition and hydrogen production in just one-step reaction process. The adsorbates of the H2O@Pt3X clusters have strong absorption in the ultraviolet and visible regions with wavelength from 300 nm to 760 nm, indicating the sunlight can be used to drive catalytic hydrolysis for producing clean hydrogen. In addition, the O atom remains on the clusters after hydrolysis and can react with CO to form CO2 in activation barrier of 0.34−0.58 eV, showing the recycling ability of the products after hydrolysis for eliminating the “poisoning” CO by oxidation. Moreover, the formed CO2 molecule can be detached from the Pt3X clusters at 323 K. Our results provide interesting guidance for practical designing the useful photocatalysts.

We report an unconventional carrier-dependent anomalous Hall effect (AHE) with a quadratic scaling relation in epitaxial films of a ferromagnetic semiconductor (ZnCo)O with a high Co concentration. We show the co-existence of AHE together with the nonlinear ordinary Hall effect (NLHE) and the separation of NLHE by using a two-conducting channels model in the expression of Hall resistivity. We found that the NLHE depends strongly on both temperature and carrier density n and dominates at low temperature when n

We report a joint experimental and theoretical study on the reactions of cobalt clusters (Co

Molecules with identical nuclei exist in nature in the form of nuclear spin isomers. Most known are the spin isomers in molecules having overall rotational symmetry. There are molecules that do not have overall rotational symmetry but instead contain symmetrical groups of atoms that perform torsion tunneling (i.e., internal rotation) around their local symmetry axes. Quantum statistics gives rise in such molecules to a specific type of spin isomers based on the torsion tunneling of symmetrical groups of atoms. Recently, enrichment and conversion of nuclear spin isomers in methanol (${\mathrm{CH}}_{3}\mathrm{OH}$) that has torsion tunneling of the methyl group was experimentally investigated by Z.-D. Sun et al. [Nat. Commun. 6, 6877 (2015)]. In the present paper a theoretical model for the methanol spin isomers and their conversion is developed. The model is based on the quantum relaxation theory confirmed to be valid for molecules with overall rotational symmetry. The methanol spin isomer conversion induced by hyperfine spin-spin and spin-rotation interactions is considered. The most important level pair for the methanol isomer conversion is found to be the $({J}^{\ensuremath{'}}=25,{K}^{\ensuremath{'}}=2,{\ensuremath{\sigma}}^{\ensuremath{'}}=1)--(J=24,K=4,p=1)$ pair in the ground torsion state ${v}_{t}=0$. The spin-rotation interaction in methanol is estimated to be equal to 1.6 kHz.

In this paper, we demonstrate the ferroelectric gate control of Rashba–Dresselhaus spin–orbit coupling (R–D SOC) in a hybrid heterostructure consisting of a ferromagnetic semiconductor channel (Zn, Co)O(0001) and a ferroelectric substrate PMN-PT(111). The R–D SOC causes a transverse spin current via the charge-spin conversion, which results in unbalanced transverse spin and charge accumulations due to the spin-polarized band in the ferromagnetic (Zn, Co)O channel. By the reversal of gated ferroelectric polarization, we observed 55% modulation of the R–D SOC correlated Hall resistivity to the magnetization correlated anomalous Hall resistivity and 70% modulation of the low-field magnetoresistance at 50 K. Our experimental results pave a way toward semiconductor-based spintronic-integrated circuits with an ultralow power consumption in ferromagnetic semiconductors.

The mixed silane films were obtained on the surface of the Q235 steel sheets by directly immersing in a mixed silane solution containing γ-Glycidoxypropyltriethoxysilane (γ-GPS) and 1, 2-bis (triethoxysilyl) ethane (BTSE), The chemical compositions and microstructures of the films were examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared spectroscopy (FTIR).The corrosion resistances were investigated by electrochemical measurements and neutral salt spray (NSS) test. The effects of silane films to the epoxy coating were investigated through the adhesive property test. The results showed that the γ-GPS/BTSE mixed silane film could remarkably improve the corrosion resistance of epoxy coating and prolong its service life.

From the perspective of vanadium battery charging-discharge efficiency, studies vanadium battery charging method by a series of charging and discharging tests, based on the principle of pulse, an pulse charging method with constant-voltage was introduced, compared with other charge method,the proposed method got the Stable discharge performance and the better charge-discharge efficiency.

Ultrasonic assisted machining has been applied in machining brittle and hard material. The critical problem of ultrasonic assisted machining is to get a proper adaptive controller of the ultrasonic vibration. In this paper, a numerical vibration model is established by a mass-damper-elastic component. The loading effect on dynamics of ultrasonic transducer is investigated. The transfer function of transducer is obtained and simulation calculation model is carried out in Matlab. The effects of different damper and elastic component on frequency characteristic of ultrasonic transducer are found. The PID algorithm and the H® algorithm for vibration control are established and simulated in the Matlab Simulink, and proves both PID algorithm and Hoo algorithm can achieve the accurate and fast controlling results. Finally, some experiments are carried out to verify the simulation calculation.

Lamb-dip spectroscopy of the C−N stretching band of methylamine has been systematically extended to P-, Q-, and R-branch by using microwave sidebands of a large number of CO2 laser lines as frequency-tunable infrared sources in a sub-Doppler spectrometer. Lamb-dip signals of more than 150 spectral lines have been observed with a resolution of 0.4 MHz and their frequencies have been precisely measured with an accuracy of ±0.1 MHz. More than 30 closed combination loops have been formed, which unambiguously confirm the assignments. For over 150 vibrational excited levels in 27 substates, refined term values have been determined and expanded in J(J + 1) power-series to determine the substate origins and the effective rotational constants. For transitions with Aa torsion-inversion symmetry in torsional state υt = 0, 57 K-doublet lines displaying asymmetry splittings have been observed and the splitting constants for levels with K = 1, 2, and 3 in the excited states have been determined. Our results provide accurate experimental information for spectroscopic studies of the interesting vibrational perturbations and intermode interactions related to the C−N stretching mode, directly support astronomical surveys, and are very relevant in practice to identification and frequency determination of the CO2-laser-pumped far-infrared laser lines of methylamine.

Reported far-infrared laser lines for five different transition systems of CH3NH2 optically pumped by a CO2 laser have been identified spectroscopically through a high-resolution Fourier transform infrared study of the C-N stretching band together with CO2-laser/microwave-sideband broad-scan and Lamb-dip measurements. From the infrared analysis plus previous far-infrared (FIR) results for the ground vibrational state, quantum numbers have been assigned for seven methylamine FIR laser transitions and their C-N stretching pump absorptions coincident with the CO2 laser lines. The assignments are confirmed through the use of closed frequency combination loops that also provide improved FIR laser frequencies to spectroscopic accuracy.

All symmetrical molecules with non-zero nuclear spin exist in nature as nuclear-spin isomers (NSIs). However, owing to the lack of experimental information, knowledge is rare about interconversions of NSIs of gaseous molecules with torsional symmetry. Here we report our separation and conversion observations on NSI-torsion-specific transition systems of gaseous methanol from a light-induced drift experiment involving partially spatial separation of the ortho and para isomers. We find that vibrationally excited molecules of the methanol spin isomer have a smaller collision cross-section than their ground-state counterparts. Interconversion of the enriched ortho isomer with the para isomer, which is generally considered improbable, has been quantitatively studied by sensitive detections of the spectral intensities. Rather counterintuitively, this reveals that the interconversion is inhibited with increasing pressure. Our results suggest that the spin conversion mechanism in methanol is via a quantum relaxation process with the quantum Zeno effect induced by molecular collisions., The conversion dynamics of nuclear-spin isomers has only been observed for a small number of molecules, generally with rotational symmetry. Here, the authors observe the separation of nuclear-spin isomers of gaseous methanol and show a decreased interconversion at higher pressures.

The infrared spectrum of the ν 11 ( a u ) out-of-plane CH 2 -wagging vibrational mode of the environmentally important 1,3-butadiene molecule has been investigated at sub-Doppler resolution with a CO 2 -laser/microwave-sideband spectrometer in order to fully resolve the rotational structure in a number of compact R Q-branch heads. The center frequencies of over 90 saturation Lamb dips in the 11 μm region have been measured with an estimated absolute accuracy of 200 kHz. The new data have been combined with previous Fourier transform results to refine the parameters in the molecular Hamiltonian. A value of |d μ c /d Q 11 |=0.3135 debye has been obtained for the transition dipole derivative for the ν 11 mode on the basis of ab initio calculations.

This work reports dual-mode operation of a broadly tunable CO2-laser/microwave-sideband spectrometer employing a Cheo waveguide modulator and a CO2 laser that can operate on hot and sequence band lines as well as low- and high-J regular band lines. The spectrometer has a broadband scanning mode at Doppler-limited resolution for spectral searching and assignment, and a narrow-band sub-Doppler mode for precision measurements. In broadband mode, a 6.7–18.5 GHz (∼0.4 cm−1) window can be covered for each sideband in a single microwave sweep with a tracking Fabry–Perot etalon filter under computer control. In sub-Doppler mode, saturation-dip spectra are obtained at sub-MHz resolution with absolute frequency measurement accuracy of the order of ±200 kHz. The instrumental performance is demonstrated via spectra of the C–O stretching fundamental vibrational band of methanol. Doppler-limited broadband scans have been recorded with good signal-to-noise ratio in both the low- and high-J regions of the 9.6-μm-CO2 lase...

We have employed a CO2-laser/microwave-sideband spectrometer to carry out saturation-dip sub-Doppler measurements of a number of 2ν2 overtone transitions of OCS in the 10-μm region. The OCS frequencies have been obtained with an absolute accuracy of order ±37 kHz, as determined from a careful analysis of the combined uncertainties in the frequency of our Lamb-dip-locked laser and the centers of the observed OCS saturation signals. Our ±37 kHz measurement accuracy is consistent with literature OCS sub-Doppler data obtained on a similar instrument. The results serve to extend the comb of precise reference frequencies in the 10-μm region and to determine the magnitudes of systematic and random uncertainties of our CO2 laser.

A CO2-laser/microwave-sideband tunable infrared source system has been newly built at the University of New Brunswick (UNB) in Canada. The system employs a high-resolution CO2 laser of Evenson design that lases on a wide range of lines including hot and sequence band lines as well as high-J lines of the regular 9.6 and 10.6 μm bands. The frequency of the CO2 laser is stabilized to the Lamb dip in the 4.3 μm fluorescence signal in an external CO2 cell. Microwave (MW) sidebands are generated in a Cheo-type infrared waveguide modulator driven by a synthesized sweeper and a traveling wave tube (TWT) amplifier. The MW sidebands appear on either side of the CO2 laser line, and are individually separated from the carrier by a tunable Fabry-Perot etalon. The sidebands currently have a typical power of about 1.4 mW and a continuous frequency tuning range of 22 GHz (from ± to ±18 GHz) when 5 W laser power and 15 W microwave power are delivered to the modulator. Details are given on the source construction and measured performance characteristics. Features of the source and its planned applications are discussed.

This note reports a useful spin-off from an infrared study of the methylamine (CH3NH2) molecule in the 10-lm region, namely a set of accurate Lamb-dip frequencies for ammonia (NH3) present as a trace constituent. The new NH3 measurements supplement previous sub-Doppler observations for ammonia [1,2] and provide an important base of standard frequencies for calibration of the methylamine CAN stretching band. CH3NH2 is a prototype nonrigid molecule with both CH3-torsion and NH2-wagging large-amplitude motions, producing complex energy structure and dense spectra [3–11] that are challenging to analyze in detail. Furthermore, due to chemical exchange with water in the absorption cell, possible slight impurity in the original samples, and even traces in the laboratory air, ammonia lines are generally present in any CH3NH2 spectrum [8–11], leading to possible confusion in the analysis [9]. In this work, using a CO2-laser-microwave-sideband spectrometer [12] in its sub-Doppler mode, saturation dips have been resolved and measured precisely for 14 NH3 lines in the m2 symmetric bending band that appear in the region of the CAN stretch of CH3NH2. The commercial CH3NH2 sample supplied by BOC Specialty Gases has a stated purity of 99.5%, so there might be an NH3 impurity of up to 0.5% given that commercial methylamine is usually prepared by the reaction of ammonia with chloromethane. The NH3 Lamb-dip signals could still be seen in our experiment even for CH3NH2 sample pressures as low as 1 mTorr, demonstrating the high sensitivity of the spectrometer. The observations are valuable in providing precise absolute frequencies for calibration of our CH3NH2 spectra, checking our measurement accuracy against a pre

A second-order quantum-mechanical torsion - rotation Hamiltonian for a molecule with two rotors has been derived by using a Taylor and Fourier series expansion on the effective total potential energy of the molecular system and on the element of inverse moment of inertia tensor in the original Hamiltonian. The effects of interactions between rotations and internal rotations, between the two rotors and also the effects of vibrations on the internal rotation barrier in a molecule with two rotors are formulated.

The sequential contact transformation technique is applied to the nuclear quadrupole coupling operator for a molecule containing a threefold symmetric internal rotor in order to be consistent with the transformed vibration–torsion–rotation Hamiltonian to be used in the analysis of the spectra of the molecule. Various higher‐order effects on the nuclear quadrupole coupling energies, such as the centrifugal distortion, the anharmonic corrections and so on, are formulated for a molecule containing one quadrupolar nucleus. The detailed discussion is presented of vibrational–torsional–rotational dependence of these higher corrections to the quadrupole hyperfine energies.

The centrifugal distortion effects for a molecule containing two symmetric internal rotors are formulated. The explicit expressions that relate the distortion constants to fundamental molecular parameters are given, which are applicable for analysing molecular structure from the parameters determined from a fit-to-observed spectrum or for calculating the centrifugal distortion constants from well known fundamental molecular parameters. The reduced torsion - rotation Hamiltonian is given for a molecule with two internal rotors with a symmetry plane which contains both internal rotation axes.

We study the spontaneously generated coherence (SGC) in a Rb atom by employing photon counting statistics based on the four-level Y-type model driven by a probe field and two coherent control fields. A transparency channel induced by coherent population trapping (CPT) and ultra-narrow probe absorption peaks in the presence of SGC are found.

We report saturation dip spectroscopy in the C-N stretching band of CH(3)NH(2) with a resolution of 0.4 MHz and an accuracy of 0.1 MHz by use of a CO(2)-laser/microwave-sideband spectrometer. The wide tunability, Lamb-dip resolution, absolute frequency accuracy, and high sensitivity of our dual-mode instrument were all key features in making precise measurements for a range of lines in the densely crowded spectrum with its complex pattern of splittings arising from the large-amplitude CH(3) torsion and NH(2) inversion. We focused on achieving resolution and assignment of transitions within the highly blended Q branch of the C-N stretch and on observations of the important K=0 sequences of Aa and Ea torsion-inversion symmetry. Term values of the latter were fitted to J(J+1) power-series expansions to obtain the K=0 C-N stretching effective B values and substate origins, from which calculated ground-state substate energies were subtracted to yield values of 1044.7061 and 1044.8011 cm(-1) for the Aa and Ea subband origins, respectively. We thereby estimate a mean value of 1044.75(5) cm(-1) for the vibrational band origin and 0.7323(5) cm(-1) for the effective upper-state B value for the C-N stretching fundamental of CH(3)NH(2).

We diagnosed the polarization characteristics of Terahertz (THz) emission from a femtosecond laser filament in air in the forward direction by using a wire grid polarizer and E-O sampling technique. The experimental results have demonstrated that the investigated THz pulse is elliptical polarized. It indicates that there is a new generation mechanism for THz emission from a laser filament other than the transition-Cherenkov radiation which is radially polarized. The generation mechanism could be through four-wave optical rectification or second-order optical rectification inside the filament due to the spatial asymmetry of the generated plasma column in the experiment.

Molecules with three or more nuclei of nonzero spin exist as discrete spin isomers whose interconversion in the gas phase is generally considered improbable. We have studied the interconversion process in ethylene by creating a sample depleted in the B 2 u nuclear spin isomer. The separation was achieved through spatial drift of this isomer induced by resonant absorption of narrow-band infrared light. Evolution of the depleted sample revealed conversion between B 2 u and B 3 u isomers at a rate linearly proportional to pressure, with a rate constant of 5.5 (±0.8) × 10 –4 s –1 torr –1 . However, almost no change was observed in the A g isomer populations. The results suggest a spin conversion mechanism in C 2 H 4 via quantum relaxation within the same inversion symmetry.

A tunable infrared (IR) source has been assembled for high-resolution molecular spectroscopy with application to environmental trace gas detection and investigation of large biomolecules. The source employs a Lamb-dip stabilized CO/sub 2/ laser of Evenson design, with 7-18 GHz microwave (MW) sidebands added via a Cheo modulator to obtain tunable IR radiation over a large fraction of the spectral band. The source will be coupled to a slit-jet molecular beam chamber for ultra-high resolution observations.

Microwave sidebands of CO2 laser lines were used as an infrared source in infrared microwave double resonance spectroscopy and infrared saturation spectroscopy to study the C -O stretching fundamental band of methanol. In the former application, rotational lines in the vCO = 1 state have been observed with good signal to noise ratios and physical processes involved in this method have been discussed. In the latter method, (vt, A/E, K) = (2, A, 4) sequence transitions in the C-O stretching fundamental band have been identified and term values for the (2, A, 4) levels in the vCO = 1 state have been determined.

The C-N stretching infrared fundamental of CH(3)NH(2) has been investigated by high-resolution laser sideband and Fourier transform synchrotron spectroscopy to explore the energy level structure and to look for possible interactions with high-lying torsional levels of the ground state and other vibrational modes. The spectrum is complicated by two coupled large-amplitude motions in the molecule, the CH(3) torsion and the NH(2) inversion, which lead to rich spectral structure with a wide range of energy level splittings and relative line intensities. Numerous sub-bands have been assigned for K values ranging up to 12 for the stronger a inversion species for the v(t) = 0 torsional state, along with many of the weaker sub-bands of the s species. The C-N stretching sub-state origins have been determined by fitting the upper-state term values to J(J + 1) power-series expansions. For comparison with the ground-state behaviour, both ground and C-N stretch origins have been fitted to a phenomenological Fourier series model that produces an interesting pattern with the differing periodicities of the torsional and inversion energies. The amplitude of the torsional energy oscillation increases substantially for the C-N stretch, while the amplitude of the inversion energy oscillation is relatively unchanged. Independent inertial scale factors ρ were fitted for the torsion and the inversion and differ significantly in the upper state. The C-N stretching vibrational energy is determined to be 1044.817 cm(-1), while the effective upper state B-value is 0.7318 cm(-1). Several anharmonic resonances with v(t) = 4 ground-state levels have been observed and partially characterized. A variety of J-localized level-crossing resonances have also been seen, five of which display forbidden transitions arising from intensity borrowing that allow determination of the interaction coupling constants.

Elliptically polarized terahertz emission from a femtosecond laser filament in air in the forward direction was discovered by using a wire grid polarizer and electro-optic sampling technique. The generation mechanism could be through four-wave optical rectification or second-order optical rectification inside the filament zone where the inversion symmetry of air is broken.

Saturation-dip measurements for the ν8 C-O stretching band of CH3OH have been systematically carried out with a CO2-laser-microwave-sideband spectrometer operating on low- and high-J 9.6 μm P-branch CO2 laser lines. Frequencies of nearly 500 spectral lines, including overlapped and doublet lines unresolved in dense Doppler-limited spectra, have been measured with a resolution of 0.4MHz and absolute accuracy of the order of ±100 kHz. Over 200 frequency combination loops have been formed from the present and previous sub-Doppler observations, unambiguously confirming the infrared transition assignments, and refined term values have been determined for 623 excited vibrational levels. These results constitute a substantial database of high-accuracy frequency reference standards for CH3OH in the 10 μm region, with applications in frequency calibration, in detailed studies of the complicated methanol intermode vibrational interactions, and in the interpretation of optically pumped far-infrared laser emission.

Microwave sidebands of CO2 laser lines were used in a sub-Doppler spectrometer to observe sub-Doppler spectrum of the C—O stretching fundamental band (vCO=1←0) of methanol. Frequencies of more than 200 vibration-rotation lines were measured with an accuracy of better than 0.20 MHz. Sixty-one blended spectral lines in the Fourier-transform spectrum were resolved with a resolution of 0.2 MHz. For transitions involving A-species levels with K=2, 3, and 4 in the vt=0 state and K=2 in the vt=1 state, 64 doublet lines arising from asymmetry splittings were observed. From these observed asymmetry splittings and calculated ground-state splittings the asymmetry splittings and asymmetry-splitting constants for the vCO=1 state were determined. The R- and Q-branch transitions for the (vt, E, K)=(1, E, 2) and (1, E, 5) sequences were assigned by observation of their Stark effects and by use of the Ritz’s combination principle. Term values of the levels in the vCO=1 state for these two sequences were given, and their Taylor-series expansion coefficients were determined.

An infrared–microwave double-resonance technique using microwave sidebands of CO2 laser lines as an infrared source has been applied for observation of rotational lines of the methanol molecule. Frequencies of more than 50 rotational lines in the excited C—O stretching vibrational state (vco=1) have been measured with good precision and have been compared with those reported in infrared studies. Many of them agree within several megahertz, although some lines show differences of >10 MHz. The pressure dependence of the double-resonance signals for two low-J microwave transitions belonging to the ground and the vco=1 states, respectively, have been observed for sample pressures as high as 0.4 Torr. For the former transition the signal has been observed to change its sign at higher pressures. Rate equation analysis explains the observed pressure dependence quantitatively and allows us to understand the physical processes involved in the double resonance.