The in-phase/quadrature phase modulation passage-acquired coherence technique(IMPACT) Fourier-transform microwave (FT-MW) spectrometer utilizing two off-axis parabolic reflectors delivers broadband capabilities at a spectral resolution similar to the resolving power of the narrowband but more sensitive coaxial beam-resonator arrangement (COBRA) FT-MW spectroscopy. Nevertheless, due to the signal pathway in the dual-path reflector arrangement, the high-frequency setup imposes a maximum applicable excitation power, thus limiting the polarization efficiency. Hence, less polar molecules were difficult to study. In a novel approach this disadvantage could be circumvented by rotating of the field vector direction of the linearly polarized microwave radiation. The setup prevails the high spectral resolution but increases the sensitivity dramatically while allowing the utilisation of very high power tube amplifiers. In this contribution we present the novel apparatus in detail as well as experimental results obtained with the modified spectrometer.

The extension of radio-frequency CMOS circuitry into millimeter wavelengths promises the extension of spectroscopic techniques in compact, power efficient systems. We are now exploring the use of CMOS millimeter devices for low-mass, low-power instrumentation capable of remote or in-situ detection of gas composition during space missions. We have chosen to develop a Flygare-Balle type spectrometer, with a semi-confocal Fabry-Perot cavity to amplify the pump power of a mm-wavelength CMOS transmitter that is directly coupled to the planar mirror of the cavity. Since the initial report last year describing the designs, we have built a pulsed transceiver system at 89-104 GHz inside a 5 cm base length cavity and demonstrated cavity finesse up to 3000, allowing for modes with 30 MHz bandwidth and a sufficient cavity amplification factor for mW class transmitters. System and component testing revealed that the power-amplifier design (embedded in the chip) was faulty and the transceiver peak power is only 10 microwatts, which is insufficient for molecular excitation on the timescale of the gas residence time within the beam. An improved power amplifier circuit has been designed and is currently under fabrication, meanwhile, we have also developed a tunable synthesizer (embedded in the same chip) that allows for tuning over the full bandwidth at increments of 10 MHz. The presentation will cover these capabilities, describing the system and component tests, as well as any new developments.

We have developed computational electrodynamics model of free induction decay (FID) signal in chirped pulse millimeter wave (CPMMW) spectroscopy. The computational model is based on finite-difference time-domain (FDTD) solution of Maxwell’s equations in 1-D. Molecular medium is represented by two-level system derived using density matrix (DM) formulation. Each cell in the grid is assigned an independent set of DM equations, and thus acts as an independent source of induced polarization. Computer simulations with our 1-D model have shown that FID signal is propagating entirely in the forward direction. Intensity of FID radiation increases linearly along the cell length. These results can be explained analytically by considering phases of electromagnetic field radiated by each independent region of induced polarization. We show that there is constructive interference in the forward in forward direction, and destructive interference in backscattering direction. Results in this study are consistent with experimental observations that FID has been measured in the forward scattering direction, but not in backscattering direction.

We present first results of a heterodyne receiver built for high-resolution emission laboratory spectroscopy of molecules of astrophysical interest. The room-temperature receiver operates at frequencies between 80 and 110 GHz, consistent with ALMA band 3. Many molecules have been identified in the interstellar and circumstellar medium at exactly these frequencies by comparing emission spectra obtained from telescopes to high-resolution laboratory absorption spectra. Taking advantage of the recent progresses in the field of mm/submm technology in the astronomy community, we have built a room-temperature emission spectrometer making use of heterodyne receiver technology at an instantaneous bandwidth of currently 2.5 GHz. The system performance, in particular the noise temperature and systematic errors, is presented. The proof-of-concept is demonstrated by comparing the emission spectrum of methyl cyanide to respective absorption spectra and to the literature. Future prospects as well as limitations of the new laboratory receiver for the spectroscopy of complex organic molecules or transient species in discharges will be discussed.

This study of the ¹³C-triply labeled species of ethyl cyanide (CH₃CH₂CN) follows our recent work on the three ¹³C-doubly-labeled that allowed their detectionMargulès, L.; et al. 2015, 69^th International Symposium on Molecular Spectroscopy, RI06n the line survey recently obtained with ALMA (EMoCA)Belloche, A.; et al. 2014, Science,  345, 1584 The detection of isotopologues could improve the knowledge of the astrochemistry. The other goal is to clean the surveys from the lines of known molecules in order to detect new ones, this is especially important for the abundant complex organic molecules like ethyl cyanide. As in the case of the doubly substitued species, no spectroscopic studies exist up to now for ¹³CH₃¹³CH₂¹³CN, the first predictions were thus obtained from scaled ab initio calculations. The spectra were recorded and analyzed up to 1 THz. More than 5500 lines were fitted with quantum numbers J and K_a up to 95 and 25 respectively.
The spectra were obtained with the new version of the Lille's solid state spectrometers. This new version used Direct Digital Synthesizer in order to speed up acquisition time. We constructed a spectrometer covering a decade, from 150 to 1500 GHz, it scans the full range in 24 hours with high sensitivity and accuracy.
This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI. This work was also done under ANR-13-BS05-0008-02 IMOLABS

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Footnotes:

Margulès, L.; et al. 2015, 69^th International Symposium on Molecular Spectroscopy, RI06i Belloche, A.; et al. 2014, Science,  345, 1584.

Plasmas used in the manufacturing processes of semiconductors are similar in pressure and temperature to plasmas used in studying the spectroscopy of astrophysical species. Likewise, the developed technology in submillimeter absorption spectroscopy can be used for the study of industrial plasmas and for monitoring manufacturing processes. An advantage of submillimeter absorption spectroscopy is that it can be used to determine absolute concentrations and temperatures of plasma species without the need for intrusive probes. A continuous wave, 500 – 750 GHz absorption spectrometer was developed for the purpose of being used as a remote sensor of gas and plasma species. An important part of this work was the optical design to match the geometry of existing plasma reactors in the manufacturing industry. A software fitting routine was developed to simultaneously fit for the background and absorption signal, solving for concentration, rotational temperature, and translational temperature. Examples of measurements made on inductively coupled plasmas will be demonstrated. We would like to thank the Texas Analog Center of Excellence/Semiconductor Research Corporation (TxACE/SRC) and Applied Materials for their support of this work.

The rotational spectrum of eugenol, the primary constituent in clove oil, was obtained via chirped-pulse Fourier transform microwave spectroscopy from 3-8 GHz in a supersonic expansion on a sample that was extracted from cloves via steam distillation. Ab initio calculations indicate that this molecule possesses several conformers with energies that are only a few hundred wavenumbers above that of the global minimum conformation, due to different relative orientations of the molecule's methoxy and allyl groups. Eugenol's spectrum was analyzed with a new version of the Autofit software that has been designed to run in cluster computing environments. Here we will present the results of this study, including benchmarking results for the new version of Autofit.

The low-energy terahertz motions of liquids greatly influence their behavior, but are not fully understood. Here, we present results from a recently developed heterodyne-detected Terahertz Kerr Effect (TKE) spectrometer, using an intense picosecond terahertz pump pulse, followed by a weak near-infrared femtosecond probe pulse. In the responses of several halomethane liquids, we find evidence for terahertz intramolecular vibrational coupling and the excitation of intermolecular motions. The experimental results are further supported by reduced density matrix and molecular dynamics simulations. With modest improvements in sensitivity, we expect this technique to be applicable to hydrogen-bonded liquids and amorphous solids.

Sub-THz vibrational spectroscopy utilizes wavelengths in the submillimeter-wave range ( 1.5-30 cm⁻¹), beyond those traditionally used for chemical and biomolecular analysis. This low energy radiation excites low-frequency internal molecular motions (vibrations) involving hydrogen bonds and other weak connections within these molecules. The ability of sub-THz spectroscopy to identify and quantify biological molecules is based on detection of signature resonance absorbance at specific frequencies between 0.05 and 1 THz, for each molecule. The long wavelengths of this radiation, mean that it can even pass through entire cells, detecting the combinations of proteins and nucleic acids that exist within the cell. This research introduces a novel sub-THz resonance spectroscopy instrument with spectral resolution sufficient to identify individual resonance absorption peaks, for the analysis of ovarian cancer cells. In vitro cell cultures of SK-OV-3 and ES-2 cells, two human ovarian cancer subtypes, were characterized and compared with a normal non-transformed human fallopian tube epithelial cell line (FT131). A dramatic difference was observed between the THz absorption spectra of the cancer and normal cell sample materials with much higher absorption intensity and a very strong absorption peak at a frequency of  13 cm⁻¹dominating the cancer sample spectra. Comparison of experimental spectra with molecular dynamic simulated spectroscopic signatures suggests that the high intensity spectral peak could originate from overexpressed mi-RNA molecules specific for ovarian cancer. Ovarian cancer cells are utilized as a proof of concept, but the sub-THz spectroscopy method is very general and could also be applied to other types of cancer.

For the past 10 years, Splatalogue has been constantly updated, modified and enhanced in order to make molecular spectroscopy data readily available to the astronomical community. Splatalogue is fully integrated into the ALMA Observing Tool, the ALMA data reduction and analysis package (CASA) and several enhanced tools being developed through the ALMA development program including the next generation CASA viewer (CARTA) and the ALMA Data Mining Toolkit (ADMIT). In anticipation for ALMA full science operations, a number of improvements have taken place over the past year to the Splatalogue database including, but not limited too, additions to Splatalogue from the JPL and CDMS line lists, improvements and reconciliation of the Lovas/NIST Catalog assigning NRAO recommended rest frequencies to every astronomically detected transition, including recent astronomical surveys to the list of transitions detected in space and finally, improved search and display features as requested by the astronomical community. Splatalogue is planning for the next 10 years of development and welcomes any and all contributions to improving the data integrity and availability to the scientific community.