The greatest strength of molecular rotational resonance spectroscopy as an analytical technique is its ability to unambiguously resolve the spectral signatures of multiple compounds, including isomers, within a mixture without requiring separation or purification. When a mixture of compounds is present, it is extremely desirable to accurately quantify each of these components. For applications in the chemical and pharmaceutical industry, a majority of the challenges in quantitative analysis are related to how the sample is handled and measured. In this talk, I will discuss our ongoing efforts to address these challenges. Some of these topics include absolute quantitation of analytes within an unknown matrix; relative quantification of a set of compounds with a difference in vapor pressure; and calibration of molecular response factors without pure reference standards.

The Dunkirk waste recovery center continuously treats all of the urban community's household waste by converting it into electrical and thermal energy through incineration. These activities are carried out with a controlled environmental impact, based on continuous improvement. The TeraWaste project explores the potential of high-resolution TeraHertz spectroscopy for continuous monitoring of gaseous emissions by developing an on-site diagnostic unit. The selectivity and the ability to detect in scattering media make it a relevant alternative to current multi-compounds monitoring solutionsG. Mouret et al., IEEE Sensors J., vol. 13, no. 1, pp. 133–138, Jan. 2013, doi: 10.1109/JSEN.2012.2227055.T. Uno et al., Jpn. J. Appl. Phys., vol. 49, no. 4S, p. 04DL17, Apr. 2010, doi: 10.1143/JJAP.49.04DL17.H. Bidgoli et al., IEEE Trans. THz Sci. Technol., vol. 4, no. 6, pp. 722–733, Nov. 2014, doi: 10.1109/TTHZ.2014.2357344. A new sub-millimeter wave source, acquired for this project and allowing the detection of trace gases, was characterized, the spectrometer developed and the detection limits of regulated compounds determined. Rotational spectroscopy measurements on real process and emission gases, sampled and analyzed off-line as well as in real time on-site, were performed and compared with standard reference methods and the certified continuous measurement system. Using preconcentrationC. F. Neese et al., IEEE Sensors J., vol. 12, no. 8, pp. 2565–2574, Aug. 2012, doi: 10.1109/JSEN.2012.2195487.N. Rothbart et al., Sensors, vol. 19, no. 12, p. 2719, Jun. 2019, doi: 10.3390/s19122719., a quantified multi-species mapping, extended to the various polar compounds absorbing the sub-mm waves of the plant's gaseous emissions, in particular VOCs by discriminating them, will enable the operator to better meet current standards and anticipate potential evolution in the regulations.

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G. Mouret et al., IEEE Sensors J., vol. 13, no. 1, pp. 133–138, Jan. 2013, doi: 10.1109/JSEN.2012.2227055.

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H. Bidgoli et al., IEEE Trans. THz Sci. Technol., vol. 4, no. 6, pp. 722–733, Nov. 2014, doi: 10.1109/TTHZ.2014.2357344.. C. F. Neese et al., IEEE Sensors J., vol. 12, no. 8, pp. 2565–2574, Aug. 2012, doi: 10.1109/JSEN.2012.2195487.

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Building block molecules with precisely controlled deuteration patterns are needed for several applications in chemistry including mechanistic studies and the production of deuterated active pharmaceutical ingredients with improved efficacy and safety. The Harman group recently reported an organometallic chemistry methodology to add deuterium to benzene with high stereoselectivity providing access to a wide range of deuteration patterns in the cyclohexene reaction product. This methodology provides access to 52 unique isotopic variants of cyclohexene covering 10 isotopologues. Establishing the stereoselectivity of the synthesis is a challenge, especially for highly deuterated substrates, and requires a technique that can quantitatively analyze both the isotopologue and isotopomer distribution in a potentially complex mixture of deuterated reaction products. Molecular rotational resonance (MRR) spectroscopy is well-suited for this analysis challenge. The application of MRR analysis to understand the stereoselectivity in the different reaction steps of the conversion of benzene to target deuterated cyclohexene reaction products is the focus of the current work. In one example, the availability of a routine, rapid isotopologue/isotopomer analysis technique is used to gain insight on the mechanistic chemistry and, subsequently, to improve the selectivity for the synthesis of cis-3,4-cyclohexene-d2. Optimization of the reaction conditions leads to the production of the target species with less than 0.1% over-deuteration and low levels of underdeuteration (mainly from the 3-cyclohexene-d1 isotopomer). The stereoselectivity of the synthesis is demonstrated by the low levels of the anti-3,4-cyclohexene-d2 isotopomer that is present at below 0.3%.

Measuring far UV light transmission through thin fluid films, methanol's absorption spectra were recorded between 150 and 220 nm (8.27-5.63 eV). Spectral changes were monitored in the function of temperature (from ambient to supercritical conditions) and pressure (at 250^oC i.e., above the supercritical point). The room temperature spectrum peak is shifted red by 4.5 nm from the previously reported position obtained by the same technique, yet agrees well with the position recorded by the attenuated total reflection (ATR) method. Unlike in water, the neat methanol spectrum shows no apparent red tail, which contradicts previous findings based on ATR studies. Upon an increase in temperature, the edge of the spectrum progressively shifts red. Still, unlike in water, this is not a symmetrical shift of the band as the lower part of the band shifts almost twice as much as the upper one, and the apparent peak position progressively shifts blue by an overall 0.13 eV upon reaching 250^oC. At this temperature, a gradual decrease of pressure from 150 to 85 bar results in continuous narrowing and red shifting of the apparent band to  7.8eV, accompanied by a steady growth of an additional broad continuum band at 6.7eV. Further decrease of pressure to 14.5 bar leads to the full emergence of the low-density spectrum of supercritical MeOH. This spectrum resembles the methanol monomer, with characteristic 1st weak absorption band at  6.7eV due to the promotion on oxygen from 2p_z (HOMO) to 3s Rydberg orbital (acquiring antibonding character along the OH vibrational coordinate) and 2nd structured band at 7.84eV due to transition between a” and the 3p Rydberg orbitals. An increase in density depresses the intensity of the first band. It has a dramatic effect on the second absorption band, in which the sharp vibrational structure gradually diminishes in magnitude and disappears above 0.1 g cm⁻³. This loss of detail cannot be explained solely by collisional broadening and/or dimerization. Still, it may suggest a gradual shift of the character of a transition from Rydberg to exciton.

Laser excitation experiments were conducted to study the energy transfer mechanisms in K-Xe mixtures with narrowband dye lasers. Specifically, the K-Xe gas mixture was excited by a tunable dye laser in the vicinity of the K D₂ line such that a population inversion on the K D₁ line was achieved. The second dye laser served as the probe and scanned around the K D₁ transition. r0pt Figure Through these experiments, the amplified probe energy is measured and the pump gain profile is obtained as shown in the spectra. The obtained data suggests than an electronic and molecular stimulated Raman scattering (SRS) process occur and compete in KXe in addition to a broad pump absorbance for emission on the K D₁ line. The Raman shift associated with the molecular SRS process of  ∼ 59 cm⁻¹ is associated with the KXe B²Σ⁺_1/2 and the dissociative X²Σ⁺_1/2 interatomic potentials. Consequently, the B²Σ⁺_1/2 and X²Σ⁺_1/2 interatomic potentials of KXe at large R can be determined by comparing experiment with calculations of the Franck-Condon integrals and quasistatistic line-broadening theory.