Rotational Spectral Lines Research Articles

A Semi-Supervised Multi-Scale Deep Adversarial Model for Fan Anomaly Detection

Failure of cooling fan will have a great impact on the operation of the air-conditioning cooling system. Traditional anomaly detection methods for fans rely on manual feature extraction, which is easy to lose effective information. Deep learning-based methods have potential to overcome such a problem, however, it is difficult to train the network without enough monitoring data. In operation, cooling usually worked at high speed, and its monitoring data contain much high-speed rotational noise. This will confuse the networks to focus on high-energy noise while lose the weak but useful information. To solve these problems, we propose a semi-supervised multi-scale deep adversarial model (SMDAM) for fan anomaly detection. In SMDAM, we propose the Linear Spectral Line Elimination (LSLE) technique to reduce the interference of rotational noise spectral lines on network training. Subsequently, a multi-scale feature extraction module is introduced to enrich diagnostic information, which extracts features from different scales without increasing the depth of the convolutional layer. Finally, two engineering data sets are used to verify the superiority of the proposed method. The results show that SMDAM is superior to other methods.

Accurately Measuring Molecular Rotational Spectra in Excited Vibrational Modes.

Although gas phase rotational spectroscopy is a mature field for which millions of rotational spectral lines have been measured in hundreds of molecules with sub-MHz accuracy, it remains a challenge to measure these rotational spectra in excited vibrational modes with the same accuracy. Recently, it was demonstrated that virtually any rotational transition in excited vibrational modes of most molecules may be made to lase when pumped by a continuously tunable quantum cascade laser (QCL). Here, we demonstrate how an infrared QCL may be used to enhance absorption strength or induce lasing of terahertz rotational transitions in highly excited vibrational modes in order to measure their frequencies more accurately. To illustrate the concepts, we used a tunable QCL to excite v3 R-branch transitions in N2O and either enhanced absorption or induced lasing on 20 v3 rotational transitions, whose frequencies between 299 and 772 GHz were then measured using either heterodyne or modulation spectroscopy. The spectra were fitted to obtain the rotational constants B3 and D3, which reproduce the measured spectra to within the experimental uncertainty of ± 5 kHz. We then show how this technique may be generalized by estimating the threshold power to make any rotational transition lase in any N2O vibrational mode.

The generation and transformation of polarization signals in molecular lines through collective anisotropic resonant scattering

ABSTRACTWe discuss the existence of elliptical polarization in rotational spectral lines of CO and other molecules within the context of the Anisotropic Resonant Scattering (ARS) model. We show that the effect of ARS on the radiation field can lead to not only the previously predicted transformation of background linear polarization into circular polarization (i.e. Faraday conversion) but also the occurrence of Faraday rotation and the generation of elliptically polarized signals in an otherwise initially unpolarized radiation field. This is due to a collective behaviour between the large number of molecules acting as a diffraction ensemble that strongly favours forward scattering over any other mode. Our application to astronomical data demonstrates the dependency of the Stokes parameters on the strength and orientation of the ambient magnetic field, and suggests that ARS will manifest itself for a wide range of molecular species and transitions.

A Terahertz Molecular Clock on CMOS Using High-Harmonic-Order Interrogation of Rotational Transition for Medium-/Long-Term Stability Enhancement

Chip-scale molecular clocks (CSMCs) perform frequency stabilization by referencing to the rotational spectra of polar gaseous molecules. With, potentially, the “atomic” clock grade stability, cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> -level volume, and <; 100-mW dc power, CSMCs are highly attractive for the synchronization of the high-speed radio access network (RAN), precise positioning, and distributed array sensing. However, the medium-/long-term stability of CSMCs is hindered by the transmission baseline tilting due to the uneven frequency response of the spectroscopic system and the molecular cell. To enhance the medium-/long-term stability, this article presents a CSMC architecture locking to the high-odd-order dispersion curve of the 231.061-GHz rotational spectral line of carbonyl sulfide (OCS) molecules, which is selected as the clock reference. A monolithic THz transceiver generates a high-precision, wavelength-modulated probing signal. Then, the wave-molecule interaction inside the molecular cell translates the frequency error between the probing signal and the spectral line center to the periodic intensity fluctuation. Finally, the CSMC locks to the third-order dispersion curve after a phase-sensitive lock-in detection. In addition, a pair of slot array couplers is employed as an effective chip-to-molecular cell interface. It leads to not only a higher SNR but also a significantly simplified CSMC package. Implemented on a 65-nm CMOS process, the high-order CSMC presents a measured Allan deviation of 4.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup> under an averaging time of τ = 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> s while consuming 70.4-mW dc power.

Physical Conditions of Gas Components in Debris Disks of 49 Ceti and HD 21997

Abstract Characterization of the gas component in debris disks is of fundamental importance for understanding their origin. To address this goal, we have conducted non-LTE (local thermodynamic equilibrium) analyses of the rotational spectral lines of CO including those of rare isotopologues (13CO and C18O) that have been observed toward the gaseous debris disks of 49 Ceti and HD 21997 with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Compact Array (ACA). The analyses have been carried out for a wide range of H2 density, and the observed line intensities are found to be reproduced as long as the H2 density is higher than 103 cm−3. The CO column density and the gas temperature are evaluated to be (1.8–5.9) × 1017 cm−2 and 8–11 K for 49 Ceti and (2.6–15) × 1017 cm−2 and 8–12 K for HD 21997, respectively, where the H2 collision is assumed for the rotational excitation of CO. The results do not change significantly even if electron collision is considered. Thus, CO molecules can be excited under environments containing no H2 or a small number of H2 molecules, even where collisions with CO, C, O, and C+ would make an important contribution to the CO excitation in addition to H2. Meanwhile, our result does not rule out the case of abundant H2 molecules. The low gas temperature observed in the debris disks is discussed in terms of inefficient heating by interstellar and stellar UV radiation.

Leading spectral moments for easy computation of pressure effects on rotational lines

AbstractExplicit classical‐limit formulae for two leading spectral moments characterizing the anisotropy of the interaction potential are derived for fast collisions of linear rotators in the binary regime. With the help of these moments, model Fourier‐transforms of the time‐correlation functions comprising non‐Markovian effects are restored, which enables a novel and straight approach to pressure transformation of broad spectral bands and pressure‐broadening characteristics of (vib)rotational spectral lines, as demonstrated on a simple Markov‐limit example of isotropic and anisotropic Raman line widths of molecular nitrogen.

Complex Organic Molecules in Taurus Molecular Cloud-1

Abstract We have observed the millimeter-wave rotational spectral lines of CH3CHO, H2CCO, cyclopropenone, and H2CO toward the cyanoployyne peak of Taurus Molecular Cloud-1 (TMC-1 CP). The spectral line profile of CH3CHO is found to reveal a well-separated double peak. It is similar to the line profile of CH3OH, but is much different from those of carbon-chain molecules and C34S. The different line profiles mean different distributions along the line of sight. The similarity of the spectral line profiles between CH3CHO and CH3OH suggests that CH3CHO is mainly formed on dust grains as CH3OH or through gas-phase reactions starting from CH3OH. On the other hand, the spectral line profiles of H2CCO and cyclopropenone are rather similar to those of carbon-chain molecules and C34S, implying their gas-phase productions. H2CO shows a composite spectral line profile reflecting the contributions of both gas-phase and grain-surface productions. In addition, we have detected the spectral lines of CH3CHO and HCOOCH3 toward the methanol peak near TMC-1 CP. We have also tentatively detected one line of (CH3)2O. Considering the chemical youth of TMC-1, the present results indicate that fairly complex organic species have already been formed in the early evolutionary phase of starless cores. TMC-1 is thus recognized as a novel source where formation processes of complex organic molecules can be studied on the basis of the line profiles.

Spectra, line intensities of the C 1Σ g + ⇒ A 1Σ u + and c 3Σ g + ⇒ a 3Σ u + transitions in liquid normal He, and rotational level populations of the C 1Σ g + and c 3Σ g + the terms

We observed the rotational spectral lines of the He*2 excimer within the range of 910–930 nm in the corona discharge in normal liquid He at the temperature of 4.2 K and the pressure of 1 atm. The spectral range is filled with the rotational lines of the C 1Σ g + ⇒ A 1Σ u + singlet and the c 3Σ g + ⇒ a 3Σ u + triplet transitions. These transitions end at the rotational levels of the lowest metastable terms, A 1Σ u + and a 3Σ u + of the He*2 excimer. Then, the population of the rotational levels with the K' number of the upper C 1Σ g + and c 3Σ g + terms (the quantity of the molecules with the rotational moment of K' in the excited molecule ensemble in the discharge) is proportional to the intensity of the rotational lines marked K' of the C 1Σ g + ⇒ A 1Σ u + singlet and the c 3Σ g + ⇒ a 3Σ u + triplet. The populations might be calculated according to the experimental intensities of the rotational spectral lines. The emitting corona plasma in the liquid He is nonequilibrium and the rotational level populations do not correspond to the Boltzmann distribution. The efficient rotational temperature exceeds the liquid He temperature, 4.2 K.

Chemical Change in the Disk Forming Region of IRAS 16293–2422 Studied with ALMA

AbstractWe have analyzed rotational spectral line emission of OCS, CH3OH, HCOOCH3, and H2CS observed toward the low-mass Class 0 protostar IRAS 16293–2422 (Source A and B) at a sub-arcsecond resolution with ALMA. Significant chemical differentiation is found at a 50 au scale. OCS is found to trace the infalling-rotating envelope, while COM distributions are concentrated around the inner part of the envelope. The kinematic structure in Source A is explained with a ballistic model, and the protostellar mass and the radius of the centrifugal barrier are evaluated to be ~0.75 M⊙ and ~50 au, respectively. This study has revealed that the centrifugal barrier plays a central role not only in the disk formation but also in the associated chemical evolution.

Pressure broadening of the electric dipole and Raman lines of CO2 by argon: Stringent test of the classical impact theory at different temperatures on a benchmark system

A classical approach is applied to calculate pressure broadening coefficients of CO2 vibration–rotational spectral lines perturbed by Ar. Three types of spectra are examined: electric dipole (infrared) absorption; isotropic and anisotropic Raman Q branches. Simple and explicit formulae of the classical impact theory are used along with exact 3D Hamilton equations for CO2–Ar molecular motion. The calculations utilize vibrationally independent most accurate ab initio potential energy surface (PES) of Hutson et al. expanded in Legendre polynomial series up to lmax = 24. New improved algorithm of classical rotational frequency selection is applied. The dependences of CO2 half-widths on rotational quantum number J up to J=100 are computed for the temperatures between 77 and 765K and compared with available experimental data as well as with the results of fully quantum dynamical calculations performed on the same PES. To make the picture complete, the predictions of two independent variants of the semi-classical Robert-Bonamy formalism for dipole absorption lines are included. This method. however, has demonstrated poor accuracy almost for all temperatures. On the contrary, classical broadening coefficients are in excellent agreement both with measurements and with quantum results at all temperatures. The classical impact theory in its present variant is capable to produce quickly and accurately the pressure broadening coefficients of spectral lines of linear molecules for any J value (including high Js) using full-dimensional ab initio - based PES in the cases where other computational methods are either extremely time consuming (like the quantum close coupling method) or give erroneous results (like semi-classical methods).

Repetitively pulsed cryogenically cooled quasi-sealed-off slab RF discharge first-overtone CO laser

A slab first-overtone CO laser of improved design excited by repetitively pulsed RF discharge was researched and developed. Its quasi-sealed-off operation appeared to be possible only by using active gas mixture composition with extremely high content of oxygen — up to 50 % with respect to CO concentration. Average output power of the first-overtone CO laser came up to ~2 W with the efficiency of ~2 %. The laser spectrum obtained by using three sets of output couplers consisted of more than 100 vibrational–rotational spectral lines in 28 vibrational first-overtone bands of CO molecule within 2.55÷3.90 μm wavelength range. The number of laser radiation pulses which could be produced by the laser in sealed-off mode of operation (without gas mixture renovation) reached ~5×105 at the averaged output power near its maximum, and ~106 at lower (near its half-maximum) averaged output power. Special features of laser radiation temporal behavior were discussed. Under repetitively pulse pump with repetition rate from 300 up to 7500 Hz, a temporal profile of the CO laser radiation changed from the train of time-separated laser pulses with high peak power to quasi-CW mode of operation.

INFALLING–ROTATING MOTION AND ASSOCIATED CHEMICAL CHANGE IN THE ENVELOPE OF IRAS 16293–2422 SOURCE A STUDIED WITH ALMA

ABSTRACT We have analyzed rotational spectral line emission of OCS, CH3OH, HCOOCH3, and H2CS observed toward the low-mass Class 0 protostellar source IRAS 16293–2422 Source A at a sub-arcsecond resolution (∼0.″6 × 0.″5) with ALMA. Significant chemical differentiation is found on a scale of 50 au. The OCS line is found to trace well the infalling–rotating envelope in this source. On the other hand, the distributions of CH3OH and HCOOCH3 are found to be concentrated around the inner part of the infalling–rotating envelope. With a simple ballistic model of the infalling–rotating envelope, the radius of the centrifugal barrier (a half of the centrifugal radius) and the protostellar mass are evaluated from the OCS data to be from 40 to 60 au and from 0.5 to 1.0 M ⊙, respectively, assuming the inclination angle of the envelope/disk structure to be 60° (90° for the edge-on configuration). Although the protostellar mass is correlated with the inclination angle, the radius of the centrifugal barrier is not. This is the first indication of the centrifugal barrier of the infalling–rotating envelope in a hot corino source. CH3OH and HCOOCH3 may be liberated from ice mantles by weak accretion shocks around the centrifugal barrier and/or by protostellar heating. The H2CS emission seems to come from the disk component inside the centrifugal barrier in addition to the envelope component. The centrifugal barrier plays a central role not only in the formation of a rotationally supported disk but also in the chemical evolution from the envelope to the protoplanetary disk.

Vibrational–rotational spectra of GaF and global multi-isotopologue analysis

In total, 521 vibrational–rotational spectral lines of the Δv=1 transitions of 69GaF and 71GaF up to bands v=5–4 and 4–3, respectively, were recorded in emission with a Fourier-transform spectrometer at unapodized resolution 0.010cm−1 in range 625–660cm−1. The response of a HgCdTe detector enforced the lower limit, 625cm−1. To calibrate accurately the spectral lines, the absorption spectrum of CO2 was simultaneously recorded, using dual sample cells, to serve as wavenumber standards. A set of 782 spectral lines comprising all present vibrational–rotational spectra of 69GaF and 71GaF, the reported laser-diode measurements of the Δv=1 band sequence and the reported rotational spectra was subjected to a global multi-isotopologue analysis through fitting with 11 isotopically invariant, irreducible molecular parameters in a single set. Normalized standard deviation 1.093 indicates a satisfactory fit. For the effects of the breakdown of the Born–Oppenheimer approximation on GaF, the values of non-Born–Oppenheimer parameters ΔBGa, ΔωGa and r1qGa(=r1qF) are experimentally determined for the first time. To facilitate the calculations or predictions of spectral frequencies, the values of the Dunham coefficients of 24 Yij and 81 band parameters for both 69GaF and 71GaF were back-calculated with uncertainties using the 11 evaluated molecular parameters. To date, various types of effective Be, re, ωe, and k have been reported for GaF. Because, in the present work, Dunham coefficients Yij are algebraically expressed with the genuine Be, ωe, ai (i=1, …) and the non-Born−Oppenheimer correction parameters, the exact expressions for the physical significance of effective quantities are derivable. The various effective quantities of Be, re, ωe and k calculated with these expressions for the physical significance and the determined values of the fitted parameters of GaF agree satisfactorily with the reported values. The physical significance of the conventional treatments of adiabatic and nonadiabatic corrections for Δ01Ga and Δ10Ga is discussed.

Quasi-bound complexes in collisions of different linear molecules: Classical trajectory study of their manifestations in rotational relaxation and spectral line broadening

Stable bimolecular complexes (tightly bound dimers) in the gas phase are usually created during third body stabilization of their unstable precursors-quasi-bound complexes (QCs). The latter can arise under the condition that at least one of the colliding partners has an internal degree of freedom. In this article, the principal difference between "orbitings" and QCs is demonstrated in the classical nonreactive scattering picture. Additionally, fractions of QCs in binary collisions of different linear molecules are compared. Also in the article the influence of QCs on rotational R-T relaxation and on vibration–rotational spectral line broadening is discussed. Explicit formulae shedding light on the QCs contribution to the R-T relaxation cross section and the line width and shift are presented. The obtained results emphasize the need for including QCs in every theoretical modeling of spectroscopic manifestation of intermolecular interactions. Besides the topics above, the possible manifestation of non-impact effects in the central regions of spectral lines due to QCs is stated. And finally, special consideration is given to the problem of adequate simulation of QCs formation at different pressures.

Pure rotational Raman lidar for absolute detection of atmospheric temperature

A pure rotational Raman lidar has become one of valid methods of profiling atmospheric temperature. However, its proper operation generally needs a certain collocated device of atmospheric temperature to calibrate three retrieval coefficients. This fact seriously restricts the applications of pure rotational Raman lidar in the meteorology and environment fields. In order to execute the detection technique of atmospheric temperature without calibration, we present and design a pure rotational Raman lidar based on the dependence of atmosphere molecular rotational Raman spectral envelope on temperature. It is configured with a laser having a pulse energy of 300 mJ, a pulse repetition rate of 20 Hz, and a Cassegrain telescope with a clear aperture of 250 mm. A two-stage multi-channel pure rotational Raman spectroscopic filter is proposed to extract efficiently the rotational Raman spectral lines with more than 70 dB suppression to the elastic-scattering optical signals. It is configured with one blazed diffraction grating, one convex lens, one linear fiber array and seven groups of fiber Bragg gratings. The blazed diffraction grating and fiber Bragg grating are separately utilized as the primary and secondary spectroscope. The tailor-made fiber array, which is composd of ten single mode fibers of 460-HP type and one multi-mode fiber, is designed to transfer the spectral signals. One end face of multi-mode fiber lies in the focal point of telescope, and then it transfers the lidar echo signals to the pure rotational Raman spectroscopic filter. The other end face of multi-mode fiber lies in the focal point of convex lens. The ten single mode fibers are used to transfer the optical signals from the primary spectroscope to the secondary, and their end faces lie in the focal plane of convex lens. Six pure rotational Raman spectral lines of nitrogen molecule in the anti-Strokes branch are chosen under the condition of the 0.09-nm forbidden band, with the consideration of the relationship between the pure rotational Raman spectral lines of nitrogen and oxygen molecules. While the excited laser wavelength is 532 nm, their central wavelengths are 530.76 nm, 529.86 nm, 529.41 nm, 528.51 nm, 527.62 nm, and 527.17 nm, respectively. Their corresponding positions of fiber end faces on fiber array are 156 m, 407 m, 532 m, 782 m, 1031 m, and 1156 m. Compared with these pure rotational Raman spectral lines, the elastic scattering signal lies on the other side of the focal point of convex lens, which improves the spectral purity of pure rotational Raman spectral lines. A retrieval algorithm of absolute detection technique is presented based on the least square principle. The performance of this lidar is simulated based on the U. S. standard atmospheric model. Simulation results show that this designed lidar can achieve the extraction of the pure rotational Raman spectral lines of nitrogen molecules, and that the atmospheric temperature profile obtained from absolute retrieval algorithm within a measurement time of 17 min can be up to 2.0 km with less than 0.5-K deviation. This pure rotational Raman lidar without calibration will provide a new detection method and retrieval scheme for atmospheric temperature profile.

R-branch and Q-branch high rotational spectral lines of diatomic molecules using improved difference converging method

The accuracies of the predicted R-branch and Q-branch transitional lines of rovibrational diatomic systems for rotational states of J 100 are improved by using new analytical formulae and an improved difference converging method (DCM) in this study. The new formulae include the contributions from a higher-order energy term Hv. The improved DCM method includes a new physical converging criterion that is particularly useful in predicting unknown transitional lines. These improvements are used to study the transitional lines of the R-branch of the TiF and CO molecules and the Q-branch of the TiF molecule. The results show that the accuracies of the R-branch and Q-branch rotational lines are about one order of magnitude better than the results obtained using previous formulae; the new physical converging criterion can efficiently reduce the possible errors in the spectrum computations; the theoretical rotational lines obtained using the improved DCM method are much better than those obtained using the least-squares method.

Study on the forward of mashgas CO temperature and concentration by the remote passive measurement

In order to reduce the second rescue injuries and deaths after the mashgas exploding in the mine, a portable imaging interferometer system is designed to detect CO temperature and concentration by the passive and remote measurement. The CO temperature and concentration are detected according to the rotational spectral line of CO gas molecule and the linear relationship between the radiation intensity of gas molecule and the molecule number density, respectively. The optical system is designed, and then its forward is studied in this work. The forward expression is obtained after studying the following four seed models of the optical system: the radiation model of target gas, where CO six emission spectral lines R11-16 are selected from HITRAN08 database; the mine CO gas transmission model in which the absorptions by the water vapor and CO2 molecule, and absorption and scattering by the mine aerosol are calculated by the relevant rules; the filter function model, in which the matched parameters of the band width of 0.5 nm and max transmittance of 0.23 for CO temperature are measured by the method of rotational line of R11-16, and the model of imaging detector CCD in which the infrared CCD of pixel 320320 and the max quantum efficiency of 0.75 are to be used in the optical system. According to the given parameters and MATLAB programming, the forward imaging interference results of CO differentiable six spectrum of R11-16 are obtained. The forward max noise-signal ratio is 268 when the exposure time is 300 s. The max electric count is 1.5105 that is larger than the selected CCD dark noise of 400 e but less than the CCD full charge quantity of 1106 e. The forward result clearly indicates that the optical system can meet the initial design demand. The accuracies of CO temperature and concentration measured by this optical system can reach 2 K and 0.1%, respectively. This portable system can be used to detect not only the mine CO, but also other gases like the pipe smoke, bomb exploding gas, etc. in which the filter and CCD need to be changed.

ABUNDANCE ANOMALY OF THE13C ISOTOPIC SPECIES OF c-C3H2IN THE LOW-MASS STAR FORMATION REGION L1527

The rotational spectral lines of c-C3H2 and two kinds of the 13C isotopic species, c- ( symmetry) and c- (Cs symmetry), have been observed in the 1–3 mm band toward the low-mass star-forming region L1527. We have detected 7, 3, and 6 lines of c-C3H2, c-, and c-, respectively, with the Nobeyama 45 m telescope and 34, 6, and 13 lines, respectively, with the IRAM 30 m telescope, where seven, two, and two transitions, respectively, are observed with both telescopes. With these data, we have evaluated the column densities of the normal and 13C isotopic species. The [c-C3H2]/[c-] ratio is determined to be 310 ± 80, while the [c-C3H2]/[c-] ratio is determined to be 61 ± 11. The [c-C3H2]/[c-] and [c-C3H2]/[c-] ratios expected from the elemental 12C/13C ratio are 60–70 and 30–35, respectively, where the latter takes into account the statistical factor of 2 for the two equivalent carbon atoms in c-C3H2. Hence, this observation further confirms the dilution of the 13C species in carbon-chain molecules and their related molecules, which are thought to originate from the dilution of 13C+ in the gas-phase C+ due to the isotope exchange reaction: . Moreover, the abundances of the two 13C isotopic species are different from each other. The ratio of c- species relative to c- is determined to be 0.20 ± 0.05. If 13C were randomly substituted for the three carbon atoms, the [c-]/[c-] ratio would be 0.5. Hence, the observed ratio indicates that c- exists more favorably. Possible origins of the different abundances are discussed.

Vibrational–rotational spectra of 13CS and global multi-isotopologue analysis

In total, 626 vibrational–rotational spectral lines of the Δv=1 transitions of 13C32S up to band v=5–4 have been measured with a Fourier-transform spectrometer at resolution 0.010cm−1. To calibrate accurately the spectral lines, a separate observation of the vibrational–rotational bands of 12C32S was made with simultaneous recording of the N2O spectrum in absorption, to serve as wavenumber standards, with dual sample cells at resolution 0.008cm−1. The spectral wavenumbers of 12C32S in turn become calibration standards. All present vibrational–rotational spectra of 13C32S and 12C32S, the reported vibrational–rotational spectra of 12C32S, 12C33S, 12C34S, and 13C32S, and the reported rotational spectra of 12C32S, 12C33S, 12C34S, 12C36S, 13C32S, 13C33S and 13C34S were subjected to a global multi-isotopologue analysis, which reduced them to molecular parameters in a single set. The wavenumbers of 3974 spectral lines, in total, comprising data of seven isotopologues were fitted with 22 isotopically invariant, traditional molecular parameters in a single set. As the normalized standard deviation is 1.38, the obtained fit is satisfactory. To facilitate the calculation of spectral wavenumbers, the values of the Dunham coefficients of 42 Yij for each of 12C32S, 12C33S, 12C34S, 12C36S, 13C32S, 13C33S, 13C34S, 13C36S, 14C32S, 14C33S, 14C34S and 14C36S, of which the spectra of the latter five isotopologues are not yet reported, were back-calculated with uncertainties using the evaluated 22 molecular parameters. The physical significance of the conventional treatments of the adiabatic and nonadiabatic corrections for Δ01C and Δ01S is discussed.

A hollow-cathode THz spectrometer for the study of astrophysical ions and radicals: Benchmarking with N2H+ and extended measurements for N2D+

Here we present the first results from a DC-discharge hollow-cathode spectrometer developed for the detection of transient species of astrophysical interest in the THz spectral regime. The new instrument was benchmarked using rotational spectral lines of N2H+ and N2D+. The known rotational lines of N2H+ were used to optimize ion formation conditions in the discharge. We then used the known spectral lines at frequencies below 700GHz to further optimize the production efficiency of N2D+, and extended spectral measurements for this ion up to ∼1THz. This resulted in the detection of four additional N2D+ rotational lines that have not been previously measured experimentally. We have used the observed line positions for N2D+ to refine the molecular parameters and extend a more accurate spectral prediction above 1THz. In addition to being excellent target molecules for benchmarking our spectrometer, N2D+ and N2H+ are commonly used as tracers of isotopic fractionation in dense interstellar clouds. Therefore, these new measurements are important for guiding astronomical observations using the high frequency bands of the new Atacama Large Millimeter Array (ALMA) and other far-IR observatories.