Andrei Deev

Hollow waveguide quantum cascade laser spectrometer as an online microliter sensor for gas chromatography

An optical absorption sensor for gas chromatography (GC) is presented. It consists of a quantum cascade laser along with a long piece of Hollow Waveguide for Infrared (HWIR) transmission inserted into the GC line. It measures the infrared absorption in each individual gas peak after separation by the GC column, and maintains the shapes of gas peaks after the HWIR sensor, making the gas samples further available for other sensors. By adding an inline combustion module before the HWIR sensor, the concentrations of many carbon containing compounds can be acquired by measuring CO2 absorption in their peaks. The HWIR sensor detects isotopologues of CO2 separately, and therefore can be used to measure carbon isotope ratios of heavy compounds. Application of the HWIR sensor to the detection of 13CO2 and CDH3 is described.

Infrared Spectra of Mass-Selected Br–—(NH3)(n) and I–—NH3 Clusters

Infrared vibrational predissociation spectra are recorded for Br(-)-(NH(3))(n) (n = 1-4) and I(-)-NH(3) clusters in the N-H stretch region (3040-3460 cm(-1)). To aid spectral assignments and clarify structures of the Br(-)-(NH(3))(n) clusters, ab initio calculations are performed at the MP2/aug-cc-pVDZ and MP2/aug-cc-pVTZ levels of theory. The Br(-)-NH(3) and I(-)-NH(3) dimers are predicted to have structures in which the NH(3) molecule is attached to the halide anion by a single hydrogen-bond. The dominant infrared band for Br(-)-NH(3) at 3171 cm(-1) corresponds to a hydrogen-bonded N-H stretch vibrational mode, whereas two weaker bands are assigned to a symmetric stretch vibration of the nonbonded N-H groups (3347 cm(-1)) and to an ammonia-based bending overtone (3293 cm(-1)) deriving infrared intensity through Fermi interaction with the H-bonded N-H stretch mode. The corresponding I(-)-NH(3) spectrum is dominated by the H-bonded N-H stretch band at 3217 cm(-1), with three weaker bands at 3240, 3305, and 3360 cm(-1) assigned to two bending overtone vibrations and the nonbonded N-H symmetric stretch vibration, respectively. Spectra of the Br(-)-(NH(3))(n), n = 2-4, clusters are similar to the I(-)-NH(3) spectrum, exhibiting evidence for strong Fermi interactions between the H-bonded N-H stretch vibrational mode and ammonia-based bending overtones. On the basis of the infrared spectra and ab initio calculations, the larger Br(-)-(NH(3))(n) clusters are deduced to have structures in which the NH(3) molecules are attached to the Br(-) by single H-bonds, but not necessarily to one other.

A field-deployable compound-specific isotope analyzer based on quantum cascade laser and hollow waveguide

A field deployable Compound Specific Isotope Analyzer (CSIA) coupled with capillary chromatogrpahy based on Quantum Cascade (QC) lasers and Hollow Waveguide (HWG) with precision and chemical resolution matching mature Mass Spectroscopy has been achieved in our laboratory. The system could realize 0.3 per mil accuracy for 12C/13C for a Gas Chromatography (GC) peak lasting as short as 5 seconds with carbon molar concentration in the GC peak less than 0.5%. Spectroscopic advantages of HWG when working with QC lasers, i.e. single mode transmission, noiseless measurement and small sample volume, are compared with traditional free space and multipass spectroscopy methods.

Quantum cascade laser sensors for online gas chromatography

We show that QC laser could improve capillary Gas Chromatography Infrared spectroscopy resolution significantly, i.e. both Doppler limited and Doppler free resolution could be achieved. To achieve these goals, we report our latest efforts in characterizing the tuning and noise properties of Quantum Cascade (QC) lasers; novel schemes on modulation to gain largest tuning range as well as on stabilizing and locking the QC lasers are proposed, and results presented.

Observation of whispering gallery modes in the mid-infrared with a quantum cascade laser: possible applications to nanoliter chemical sensing

Excitation of the whispering gallery modes (WGM) of a CaF2 ball resonator is demonstrated at 4.5 micron with a pulsed Quantum Cascade laser. A prism coupling scheme for mid-infrared is described. Future applications of WGM resonators as hyphenated inline chromatography sensors are discussed.

A minimized ultra-sensitive MIR hollow waveguide (HWG) isotope ratio analyzer for environmental and industrial applications

An advanced commercial InfraRed Isotope Ratio (IR2) analyzer has been developed in Arrow Grand Technologies and the hollow waveguide (HWG) is used as the sample tube. By measuring the selected CO2 absorption peaks in the Mid- IR(MIR), the stable carbon isotope ratio, i.e. 13C, is obtained at a fast sampling rate. Combined with a GC and a combustor, it has been successfully employed to measure compound specific 13C isotope ratios in the field. By updating the single path HWG to 5-path HWG, we have also demonstrated its application for the environmental and health research. Here, the isotope ratio analyzer is minimized in size and weight to better fulfill the field deployment requirements. The size is reduced from 80cm*51cm*51cm to 74cm*33cm*46cm. After optimizing all subsystems, the minimized isotope ratio analyzer has a better performance. What’s more, the number of HWG paths can be selected to match the specific application. For instance, a 3-pass HWG is selected to conduct ultra-sensitive compound specific isotope analysis for mud gas logging, and a 5+1 pass HWG could measure isotope ratios of carbon with an ultra-broad CO2 concentration range of 300 ppm-47,500 ppm and a fast sample refresh and data processing rate up to 10Hz.

MIR hollow waveguide (HWG) isotope ratio analyzer for environmental applications

An advanced commercial Mid-InfraRed Isotope Ratio (IR2) analyzer was developed in Arrow Grand Technologies based on hollow waveguide (HWG) as the sample tube. The stable carbon isotope ratio, i.e. δ13C, was obtained by measuring the selected CO2 absorption peaks in the MIR. Combined with a GC and a combustor, it has been successfully employed to measure compound specific δ13C isotope ratios in the field. By using both the 1- pass HWG and 5-path HWG, we are able to measure δ13C isotope ratio at a broad CO2 concentration of 300 ppm-37,500 ppm. Here, we demonstrate its applications in environmental studies. The δ13C isotope ratio and concentration of CO2 exhaled by soil samples was measured in real time with the isotope analyzer. The concentration was found to change with the time. We also convert the Dissolved Inorganic Carbon (DIC) into CO2, and then measure the δ13C isotope ratio with an accuracy of better than 0.3 ‰ (1 σ) with a 6 min test time and 1 ml sample usage. Tap water, NaHCO3 solvent, coca, and even beer were tested. Lastly, the 13C isotope ratio of CO2 exhaled by human beings was obtained <10 seconds after simply blowing the exhaled CO2 into a tube with an accuracy of 0.5‰ (1 σ) without sample preconditioning. In summary, a commercial HWG isotope analyzer was demonstrated to be able to perform environmental and health studies with a high accuracy (~0.3 ‰/Hz1/2 1 σ), fast sampling rate (up to 10 Hz), low sample consumption (~1 ml), and broad CO2 concentration range (300 ppm-37,500 ppm).

The gas isotope interpretation tool: A novel method to better predict production decline

ABSTRACT Production decline prediction is important to understand the performance and life span of oil and gas wells. The most common prediction method is decline curve fitting based on available production rate data. Such data are fit with different equations that extrapolate to future time. However, the parameters are commonly poorly constrained, especially when the production rate data are limited. In this study, we establish a novel gas isotope interpretation tool to better predict the resource quantity and life span of producing gas wells. This tool is based on the evolution of methane carbon isotope ratios ( δ 13 C1) caused by different gas-releasing processes during production. It requires (1) real-time methane carbon isotope ratio data, (2) continuous gas production rate data for a certain period of time, and (3) basic geological and engineering conditions. We successfully applied the production decline prediction tool to a producing shale gas well in the Barnett Shale. We obtained real-time δ 13 C1 data for approximately 1 yr using our proprietary, field-deployable gas chromatography–infrared isotope ratio analyzer. The prediction in this well from the isotope method showed a total reserve of up to 7.34–7.75 BCF (2.07–2.19 × 10 8 m 3 ), which was used to constrain the production decline trend of the study well. The measured production rate data were first fit using the Arps equation, which then joined to an exponential decline curve smoothly at approximately 10 yr, such that the cumulative production calculation from integration of the product rate curve equaled to the total reserve predicted by the isotope method. The novel production decline prediction method thus provided important constraint on the future well production and expected ultimate recoverable reserves.

Field test results of compound specific isotope analyzer based on quantum cascade lasers and hollow waveguide

The first of its kind Gas Chromatograph Infra Red Isotope Ratio (GC-IR2) instruments have been deployed to the field to help the identification of sweet spot during the shale gas exploration. The onsite measurement capability of the GC-IR2 along with its accuracy and speed helped the discovery of the fast dynamics of gas release from shale cuttings. The half life of the isotope change for methane, ethane and propane released from shale cuttings is closely related to the porosity and permeability of the specific shale reservoir, and could be as short as a one hour to a couple of days. Initial δ13C values for methane could be extremely fractionated toward heavy 13C species that values in the -20~<-10 per mil, which belong to inorganic methane could be measured.

Polarization and isolation control for quantum cascade lasers in the mid-infrared

There have been limited choices of optical materials in the Mid-Infrared for polarization control and subsequent isolation. We show several combinations of existing materials and optics that could realize polarization control and isolation for quantum cascade lasers in the MIR. Improvements in signal to noise ratio in MIR laser spectroscopy, as well as saturated absorption spectroscopy utilizing the isolation achieved, will be discussed.