In the present work, we have investigated the rotational spectrum of the ν7 = 1 vibrational state of CH2OO in the 250-500 GHz range, produced by photolysis of the CH2I2 precursor in the presence of O2. In order to carry out such an investigation, we have developed a new experimental setup that combines UV pulsed laser photolysis and a room-temperature flow cell with a Fourier-transform millimeter-wave emission spectrometer. A multiple-pulse acquisition protocol enables time-resolved detection of transient species over millisecond time scales to improve signal-to-noise ratios through averaging. This system enables in situ observation of transient species and their vibrationally excited states under thermal conditions, demonstrating the capabilities of a new instrument that can record time-resolved rotational spectra. A total of 120 transitions were measured and used to determine accurate spectroscopic parameters for CH2OO (ν7 = 1).

We have started a measurement campaign of numerous methanol isotopologs in low-lying torsional states in order to provide extensive line lists for radio astronomical observations from an adequate spectroscopic model and to investigate how the intricate vibrationtorsion-rotation interactions manifest themselves in the spectra of different isotopic species. After CD3OH and CD3OD, we turn our focus to CH3OD, which is an important species for studying deuteration in prestellar cores and envelopes that enshroud protostars. Notably, deuteration is frequently viewed as a diagnostic tool for star formation. The measurements used in this study were obtained in two spectroscopic laboratories and cover large fractions of the 34 GHz-1.35 THz range. As done in previous studies, we employed a torsion-rotation Hamiltonian model for our analysis that is based on the rho-axis method. The resulting model describes the ground and first excited torsional states of CH3OD well up to quantum numbers J <= 51 and K-a <= 18. We derived a line list for radio astronomical observations from this model that is accurate up to at least 1.35 THz and should be sufficient for all types of radio astronomical searches for this methanol isotopolog in these two lowest torsional states. This line list was applied to a reinvestigation of CH3OD in data from the Protostellar Interferometric Line Survey of IRAS 16293-2422 obtained with the Atacama Large Millimeter/submillimeter Array. The new accurately determined value for the column density of CH3OD implies that the deuteration in methanol differs in its two functional groups by a factor of similar to 7.5.

ABSTRACT The main isotopologue of 2-hydroxyacetonitrile (glycolonitrile; HOCH2CN) has recently been detected in the interstellar medium (ISM). To date, no rotational spectroscopy of 2-hydroxyacetonitrile 13C-isotopologues studies has been carried out and only few centimetre-wave measurements of one deuterated isotopologue (DOCH2CN) exist. The rotational spectrum of the 2-hydroxyacetonitrile 13C-isotopologues and DOCH2CN was investigated from 150 to 530 GHz. As the parent isotopic species, the other 2-hydroxyacetonitrile isotopologues exhibit large amplitude motion due to the torsion of the hydroxyl group. The analyses of the spectra were carried out using the reduced axis system (RAS) formalism and Watson’s S-reduction Hamiltonian implemented in the spfit code. More than 3000 lines were fitted for the three studied isotopologues, with quantum number values reaching 60–67 for J and 21–25 for Ka depending on the species. Accurate line lists up to 600 GHz and partition functions are provided. A search for these isotopologues in SMM1-a and IRAS 16293 B surveys resulted in non-detections; upper limits to the column density were determined. The accurate spectroscopic prediction of their spectra provided in this work will allow astronomers to continue the search for 2-hydroxyacetonitrile isotopologues in the ISM.

Context. Methylamine (CH3NH2) was first detected in the interstellar medium (ISM) toward Sgr B2 almost 50 years ago by observation of rotational transitions in its torsional ground state. Methylamine exhibits two large-amplitude motions (LAMs), the methyl torsion and amine wagging, which complicate the spectral analysis, especially in excited vibration states. The lack of an accurate model of the two coupled LAMs has also hampered the identification in the ISM of rotational transitions in excited vibrational states. Aims. The aim of this work is to study the terahertz and microwave rotational spectra of methylamine experimentally and theoretically in order to provide a reliable basis for the detection of its rotational transitions in the first torsionally excited state, υt = 1, in the ISM. Methods. The terahertz spectrum of methylamine was measured from 150 to 1520 GHz with the Lille fast scan spectrometer. Using a new “hybrid” Hamiltonian model, we were able to analyze the nuclear quadrupole hyperfine structure and to accurately fit the rotational spectrum of the υt = 1 state of methylamine. We used the imaging spectral line survey ReMoCA performed with the Atacama Large Millimeter/submillimeter Array (ALMA) to search for rotational transitions of methylamine in its first torsionally excited state toward the high-mass star forming region Sgr B2(N). The observed spectra are modeled under the assumption of local thermodynamic equilibrium (LTE). Results. Accurate spectral predictions were obtained for the ground and first excited states of CH3NH2. We report the first interstellar detection of methylamine in the υt = 1 state toward the offset position Sgr B2(N1S) in the hot molecular core Sgr B2(N1). The LTE parameters derived previously from the rotational emission of methylamine in its torsional ground state toward Sgr B2(N1S) yield synthetic spectra of methylamine in the υt = 1 state that are fully consistent with the ALMA spectra and allow us to identify five rotational lines of this state.

Subject and Purpose. Results are presented of the recent considerable upgrade implemented at the Kharkiv microwave spectrometer. The upgrade has been aimed at extending the operating frequency range and increasing the utmost accessible spectral resolution of the spectrometer. Methods and Methodology. In order to extend the frequency range we have designed and constructed new BWO-based oscillator units, also providing for possibility of frequency tripler application. Construction of a new absorbing cell of enlarged diameter allowed us to considerably improve the spectral resolution for Lamb-dip measurements. Results. Owing to the upgrade, the spectrometer has become able to cover the frequency range from 34 to 420 GHz, with a gap from 183 to 200 GHz. The spectral resolution in the Lamb-dip observation mode has been increased by a factor of two. In addition, the functionality of the spectrometer has been significantly improved via modernization of several of its subsystems. Conclusions. The new upgrades of the spectrometer systems have permitted extending the operational frequency range and increasing the utmost accessible resolution by means of reducing the time-of-flight line broadening in the Lamb-dip measurements. In addition, application of square-wave frequency modulation with accurately known modulation parameters, in combination with careful modeling of the distortions caused by reflections in the absorbing cell, has allowed us to significantly improve the accuracy of line frequency measurements.

Solar-type prestellar cores and protostars display large amounts of deuterated organic molecules. Recent findings on CHD$_2$OH and CD$_3$OH toward IRAS 16293-2422 suggest that even fully deuterated methanol, CD$_3$OD, may be detectable as well. However, searches for CD$_3$OD are hampered in particular by the lack of intensity information from a spectroscopic model. The objective of the present investigation is to develop a spectroscopic model of CD$_3$OD in low-lying torsional states that is sufficiently accurate to facilitate searches for this isotopolog in space. We carried out a new measurement campaign for CD$_3$OD involving two spectroscopic laboratories that covers the 34 GHz-1.1 THz range. A torsion-rotation Hamiltonian model based on the rho-axis method was employed for our analysis. Our resulting model describes the ground and first excited torsional states of CD$_3$OD well up to quantum numbers $J \leq 51$ and $K_a \leq 23$. We derived a line list for radio-astronomical observations from this model that is accurate up to at least 1.1 THz and should be sufficient for all types of radio-astronomical searches for this methanol isotopolog. This line list was used to search for CD$_3$OD in data from the Protostellar Interferometric Line Survey of IRAS 16293$-$2422 obtained with the Atacama Large Millimeter/submillimeter Array. While we found several emission features that can be attributed largely to CD$_3$OD, their number is still not sufficiently high enough to establish a clear detection. Nevertheless, the estimate of 2$\times 10^{15}$ cm$^{-2}$ derived for the CD$_3$OD column density may be viewed as an upper limit that can be compared to column densities of CD$_3$OH, CH$_3$OD, and CH$_3$OH. The comparison indicates that the CD$_3$OD column density toward IRAS 16293-2422 is in line with the enhanced D/H ratios observed for multiply deuterated complex organic molecules.

We present the results of our new study of the torsion-rotation spectrum of the acetamide molecule, CH3CONH2. Despite the fact that acetamide was found to be quite abundant in the interstellar medium, its rotation spectrum was studied only up to $J_{\max}=20$ so far. The aim of the present study was to extend the quantum number range involved in the analysis (thus improving the quality of predictions for higher excited rotational states) as well as the frequency range coverage. The new measurements were carried out from the millimeter wave range (starting at 34.5 GHz) to the sub-millimeter wave range (up to 645 GHz) using spectrometers in the Kharkiv and Köln laboratories. Our preliminary fits of the $v_{\mathrm{t}}=0,1,2$ torsional states of acetamide with $J_{\max}=62$ revealed some perturbations, which we attribute to distortions caused by the NH2 wagging state at ∼259 cm−1 (that propagate down to low-lying torsional states via intertorsional interactions). The extension of our assignments to the third excited torsional state of acetamide is a preparatory step toward explicitly accounting for interactions with the NH2 wagging state of acetamide. So far, 421 A-type and 263 E-type rotational transitions up to $J=32$ belonging to the third excited torsional state of acetamide were assigned and added to the analysis. A joint $v_{\mathrm{t}}=0,1,2,3$ dataset involving 8240 rotational transitions was fit using the rho axis method giving a weighted root mean square deviation of 2.8 for a Hamiltonian model that includes 114 parameters.

We present a project of a new DDS-based multi-functional spectrometer and the results of its partial implementation. The proposed instrument may be rather quickly transformed from an absorption spectrometer to an emission one. Multi-functionality of proposed solution allows one to benefit from the strong features of different spectroscopic techniques depending on the goals of performed spectroscopic study. The emission spectroscopy techniques may be applied to reach the highest sensitivity or allow studying of non-stationary objects with a segmented chirped-pulse mode. The absorption spectroscopy techniques may be applied to reach the highest resolution and accuracy via Lamb-dip measurements or allow traditional studying of molecular spectra with Doppler-limited resolution.

Solar-type protostars have been shown to harbor highly deuterated complex organics, as evidenced, for instance, by the high relative abundances of doubly and triply deuterated isotopologs. While this degree of deuteration may provide important clues in studying the formation of these species, spectroscopic information on multiply deuterated isotopologs is often insufficient. In particular, searches for triply deuterated methanol, CD 3 OH, are hampered to a large extent by the lack of intensity information from a spectroscopic model. The aim of the present study is to develop a spectroscopic model of CD 3 OH in low-lying torsional states that is sufficiently accurate to facilitate further searches for CD 3 OH in space. We performed a new measurement campaign for CD 3 OH involving three spectroscopic laboratories that covers the 34 GHz−1.1 THz and the 20−900 cm −1 ranges. The analysis was performed using the torsion-rotation Hamiltonian model based on the rho-axis method. We determined a model that describes the ground and first excited torsional states of CD 3 OH, up to quantum numbers J ≤ 55 and K a ≤ 23, and we derived a line list for radio-astronomical observations. The resulting line list is accurate up to at least 1.1 THz and should be sufficient for all types of radio-astronomical searches for this methanol isotopolog. This line list was used to search for CD 3 OH in data from the Protostellar Interferometric Line Survey of IRAS 16293−2422 using the Atacama Large Millimeter/submillimeter Array. Specifically, CD 3 OH is securely detected in the data, with a large number of clearly separated and well-reproduced lines. We not only detected lines belonging to the ground torsional state, but also several belonging to the first excited torsional state. The derived column density of CD 3 OH and abundance relative to the non-deuterated isotopolog confirm the significant enhancement of this multiply deuterated variant. This finding is in line with other observations of multiply deuterated complex organic molecules and may serve as an important constraint on their formation models.

Subject and Purpose. The frequency modulation (FM)combined with lock-in detection, the technique which is used in microwave spectroscopy for enhancing the sensitivity of measurements, as well as the effects due to standing wavesinthe measuring absorption cell can lead to distortions in the spectral line shapes observed. To ensure the highest possible accuracy derivable from the experimental data, these distortions needto be taken into account. A way of improving theaccuracy is to approximate to the experimental line contour with a theoretical line shape that would account for the observable distortion effects.The relevant literature sources suggest examples of theoretical expressions for the line shape in the case of a sinusoidal frequency modulation. This work has been aimed at derivingsimilar expressions for the case of a square-wave frequency modulation that shall allow increasing the accuracy of measurements. Methods and Methodology.The square-wave-FM signalsare obtained with the aid of a direct digital frequency synthesizer thatcan provide switching between two frequencies known to a high accuracy. This technical solution permits generating FM signals with precisely specified parameters. Results. A closed-form expression has been suggested, based on numerically evaluated line shape derivatives, whichallows taking into considerationthe basic types of distortions encountered in the spectral line records. The cases that have been considered concern a variety of experimental conditions, including sub-Doppler measurements with Lamb-dip observations. Conclusions. The approach that has been proposed allows one to properly take into account the distortions of spectral line shapes resulting from the use of a square-wave-FM signal, as well as those due to standing wave effects in the spectrometer cell. As has been found, application of this approach to experimental spectra with a variety of modulation parameters permits reducing the errors of frequency determination to ±0.001MHz, provided the signal-to-noise ratios are reasonably high.

The results of the study of the MARK-4B antenna system of RT -32 radio telescope functional capabilities in S- and X-band are presented. The frequency bands for effective antenna system operation were determined in the study. A theoretical and experimental study of the corrugated feed horn operation possibilities in the S- and X-band has been carried out. The radiation pattern of the antenna system was measured using the Cygnus A radio source in two frequency subranges of the X-band. It is shown that the antenna system can work effectively in the found frequency subranges of S-and X-band. Some promising options for design of a waveguide system for separating S-/X-band signals with orthogonal polarizations are presented.

We present b the results of our new study of the torsion-rotation spectra of the two deuterated isotopologues of methanol: CD 3 OH and CH 3 OD.The new microwave measurements were carried out from the millimeter wave range (starting at 34 GHz) to the THz range (up to 1.1 THz) using spectrometers in Kharkiv and Köln.The new measurements in the FIR range were carried out in Braunschweig for CD 3 OH from 20 to 900 cm -1 .In this work we significantly extend the rotational quantum number coverage for both isotopologues (from J up = 26 [1] to J up = 55 for CD 3 OH and from J up =21 [2] to J up =40 for CH 3 OD).The analysis is done using the rho axis method and the RAM36 program code.Our preliminary fits show that for both isotopologs the v t = 2 torsional state is significantly affected by intervibrational interactions with non-torsional vibrational modes which propagate down through intertorsional interactions.At the same time, for CD 3 OH we were able to get a fit within experimental error for v t = 0, 1 states.For CH 3 OD analysis is in progress now.In the talk the details of this new study will be discussed.

Peptide bonds, as the molecular bridges that connect amino acids, are crucial to the formation of proteins. Searches and studies of molecules with embedded peptide-like bonds are thus important for the understanding of protein formation in space. Here we report the first tentative detection of propionamide (C 2 H 5 CONH 2 ), the largest peptide-like molecule detected in space toward Sagittarius B2(N1) at a position called N1E that is slightly offset from the continuum peak. New laboratory measurements of the propionamide spectrum were carried out in the 9–461 GHz range, which provide good opportunity to check directly for the transition frequencies of detected interstellar lines of propionamide. Our observing result indicates that propionamide emission comes from the warm, compact cores in Sagittarius B2, in which massive protostellars are forming. The column density of propionamide toward Sgr B2(N1E) was derived to be 1.5 × 10 16 cm −2 , which is three-fifths of that of acetamide, and one-nineteenth of that of formamide. This detection suggests that large peptide-like molecules can form and survive during star-forming process and may form more complex molecules in the interstellar medium (ISM). The detection of propionamide bodes well for the presence of polypeptides, as well as other complex prebiotic molecules in the ISM.

To improve sensitivity of absorption spectrometers a source modulation with lock-in detection is usually employed.In the Kharkiv millimeter wave spectrometer we employ DDS based square-wave frequency modulation which is characterized by a high certainty of modulation parameters.Commonly applied approaches developed for a sine-wave frequency modulation (see for example [1]) are not able to fully account for all lineshape modifications due to the square-wave frequency modulation.That is why we have developed a new expression which allows us to take into account lineshape modification due to square-wave frequency modulation as well as well-known problem of lineshape distortions caused by presence of standing wave in an absorbing cell.Our approach reproduce well observed line profiles and as the result provides some improvement of measurement accuracy.In the talk the details of the new approach will be discussed.

Three compounds with a C3H6O2 formula have been detected in the Interstellar Medium (ISM): ethyl formate (CH3CH2OC(O)H), methyl acetate (CH3OC(O)CH3) and very recently hydroxyacetone (CH3C(O)CH2OH). The higher thermodynamic stability of another isomer, the propanoic acid (CH3CH2C(O)OH), clearly suggests that this molecule should be considered as a possible candidate for ISM detection. To provide reliable predictions for astronomical use in the millimeter and submillimeter wave ranges we performed a new study of propanoic acid rotational spectrum up to 545 GHz. The analysis of large amplitude methyl top torsional motion in this molecule was carried out using the rho axis method and the RAM36 program code. More than 3200 lines corresponding to the rotational transitions in the ground and first excited methyl top torsional states were newly assigned and fit within experimental error. This enabled us to produce new predictions which were used to search for propanoic acid in two high-mass star-forming regions: SgrB2 (public IRAM 30 m) and Orion KL (ALMA Science Verification). We report a non-detection of propanoic acid in these clouds and derive upper limits to the column density.

Solar-type protostars harbor highly deuterated complex organics. While this degree of deuteration may provide important clues in studying the formation of these species, spectroscopic information on multiply deuterated isotopologs is often insufficient. In particular, searches for triply deuterated methanol, CD_3OH, are hampered by the lack of intensity information from a spectroscopic model. The aim of the present study is to develop such a model of CD_3OH in low-lying torsional states that is sufficiently accurate to facilitate further searches for CD_3OH in space. We performed a new measurement campaign for CD_3OH involving three spectroscopic laboratories that covers the 34 GHz-1.1 THz and the 20-900 cm^-1 ranges. The analysis was performed using the torsion-rotation Hamiltonian model based on the rho-axis method. We determined a model that describes the ground and first excited torsional states of CD_3OH, up to quantum numbers J ⩽ 55 and K_a ⩽ 23, and we derived a line list for radio-astronomical observations. This list is accurate up to at least 1.1 THz and should be sufficient for all types of radio-astronomical searches for this methanol isotopolog. It was used to search for CD_3OH in data from the Protostellar Interferometric Line Survey of IRAS 16293-2422 using ALMA. CD_3OH is securely detected in the data, with a large number of clearly separated and well-reproduced lines. We detected lines belonging to the ground and the first excited torsional states. The derived abundance of CD_3OH relative to non-deuterated isotopolog confirm the significant enhancement of this multiply deuterated variant. This finding is in line with other observations of multiply deuterated complex organic molecules and may serve as an important constraint on their formation models.