Single-line Spectrum Research Articles

The study of dosimetric properties of sulfanilic acid in low radiation dose range using the ESR technique

The development of new dosimeters with good dosimetric properties is important for quality control in radiation applications. In this study, the potential of sulfanilic acid (C6H7NO3S) powder form, as a dosimeter in low-dose ionizing radiation (<30 Gy), was analyzed by an Electron Spin Resonance spectrometer (Bruker EMX-131 X-band). Gamma irradiations were performed at room temperature (290 K) using a 60Co gamma cell supplying a dose rate of 32 Gy/h and X photon irradiations at 6 and 18 MV energies were performed using a variant DHX model clinical linear accelerator (Linac) at a dose rate of 3 Gy/min. While unirradiated (control) sulfanilic acid exhibited no ESR signal, the irradiated sample showed a single-line ESR spectrum spread over a magnetic field range of 100 G, as shown in Figure 2. Variations of the peak heights with the sample mass irradiated at 2 Gy gamma dose were studied in the range of 130–330 mg. The ESR signal intensity observed at g-factor = 2.0053 of this compound is dependent on sample mass, so ∼250 mg was chosen at each step of the study. The paramagnetic center formed in the gamma-irradiated sulfanilic acid was followed over 50 days. The dose-response curves were given in the dose range from 0.05 to 10 Gy for the sample exposed to gamma radiation and for the sample exposed in the range of 0.05 Gy–30 Gy at 6 and 18 MV X-ray energies. The fitting values of the function that best describes dose-response curves are calculated. In the g value region, where the ESR signal was observed in the irradiated sample, the lowest dose value at which the signal could be read was 50 mGy, significantly different from the noise. With all these investigations, sulfanilic acid can be used to estimate gamma radiation dose within boundary conditions in medical applications.

Active vibration control using nonlinear auto-regressive neural network to identify secondary channel

The power unit on board the ship generates periodic low-frequency vibration that affects the normal operation of the equipment on board, and the adaptive feedforward control algorithm can effectively suppress such harmful vibration noise. But the adaptive feedforward control algorithm needs to obtain the identification model of the secondary channels, and the frequency domain least squares method based on the linear Extended auto-regressive model (ARX) is difficult to obtain the identification model with nonlinear characteristics. The nonlinear auto-regressive model (NARX) adds nonlinear mapping layers to the topology of the ARX model to enhance the identification capability of the NARX model for complex systems. In this paper, a block diagram of the Fx-LMS feedforward control algorithm based on the NARX model is proposed, then the initial parameters of the NARX neural network are optimized using the Quantum Particle Swarm Optimization (QPSO) algorithm and the secondary channel is identified, and the identification results show that the accuracy of identifying the secondary channel using the NARX neural network is higher than that of the ARX model. The simulation and experimental results show that the vibration damping effect of the proposed method is better than the traditional Fx-LMS method for both single-line spectrum and multi-line spectrum periodic low-frequency disturbances, which provides a new method for the suppression of periodic low-frequency disturbances.

Hot Subdwarf Stars Identified in LAMOST DR8 with Single-lined and Composite Spectra

A total of 222 hot subdwarf stars were identified with LAMOST DR8 spectra, among which 131 stars show composite spectra and have been decomposed, while 91 stars present single-lined spectra. Atmospheric parameters of all sample stars were obtained by fitting hydrogen (H) and helium (He) line profiles with synthetic spectra. Two long-period composite sdB binaries were newly discovered by combining our sample with the non-single-star data from Gaia DR3. One of the new systems presents the highest eccentricity (i.e., 0.5 ± 0.09) among known wide sdB binaries, which is beyond model predictions. A total of 15 composite sdB stars fall in the high-probability binary region of the RUWE−AEN plane and deserve priority follow-up observations to further study their binary nature. A distinct gap is clearly presented among temperatures of cool companions for our composite-spectrum sample, but we could not come to a conclusion as to whether this feature is connected to the formation history of hot subdwarf stars before their binary natures are confirmed.

A White Dwarf–Main-sequence Binary Unveiled by Time-domain Observations from LAMOST and TESS

We report a single-lined white dwarf–main-sequence binary system, LAMOST J172900.17+652952.8, which is discovered by the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST)’s medium-resolution time-domain surveys. The radial-velocity semi-amplitude and orbital period of the optical visible star are measured by using follow-up observations with the Palomar 200 inch telescope and light curves from the Transiting Exoplanet Survey Satellite (TESS). Thus the mass function of the invisible candidate white dwarf is derived, f(M 2) = 0.120 ± 0.003 M ⊙. The mass of the visible star is measured based on a spectral energy distribution fitting, M 1 = . Hence, the mass of its invisible companion is M 2 ≳ 0.63 M ⊙. The companion ought to be a compact object rather than a main-sequence star owing to the mass ratio q = M 2/M 1 ≳ 0.78 and the single-lined spectra. The compact object is likely to be a white dwarf if the inclination angle is not small, i ≳ 40°. By using the Galaxy Evolution Explorer (GALEX) near-UV flux, the effective temperature of the white dwarf candidate is constrained as ≲ 12,000–13,500 K. It is difficult to detect white dwarfs which are outshone by their bright companions via single-epoch optical spectroscopic surveys. Therefore, optical time-domain surveys can play an important role in unveiling invisible white dwarfs and other compact objects in binaries.

Parameter Estimation for Quantitative EPR Spectroscopy

Electron paramagnetic resonance (EPR) is a spectroscopy and imaging method based on detecting the spin resonance of electrons. EPR is particularly suited for detecting and quantifying free radicals and biological markers of oxidative stress, for which it is the only quantitative imaging method at the moment. Its application in clinical contexts is a major challenge because of the lack of standardized procedures for estimating the measurement quality. Previous work analyzed the Lorentzian model of single-line EPR spectra in the derivative limit. For the general case, a modified acquisition procedure called overmodulation improves the signal-to-noise ratio (SNR). This article studies single-line EPR spectra with Lorentzian line shape under overmodulation and proposes maximum likelihood estimates (MLEs) as well as formulas for the expected relative error. The results are validated with simulated spectra and in vitro experimental results. The computed relative error is shown to be a good estimate of the observed instrumental variation.

Hot Subdwarf Stars Identified in Gaia DR2 with Spectra of LAMOST DR6 and DR7. I. Single-lined Spectra

Abstract 182 single-lined hot subdwarf stars are identified by using spectra from the sixth and seventh data releases (DR6 and DR7) of the Large Sky Area Multi-Object Fibre Spectroscopic Telescope survey. We classified all the hot subdwarf stars using a canonical classification scheme, and got 89 sdB, 37 sdOB, 26 sdO, 24 He-sdOB, 3 He-sdO, and 3 He-sdB stars, respectively. Among these stars, 108 hot subdwarfs are newly discovered, while 74 stars were reported by previous catalogs. The atmospheric parameters of these stars were obtained by fitting the hydrogen (H) and helium (He) lines with non-local thermodynamic equilibrium model atmospheres. The atmospheric parameters confirm the two He sequences and the two subgroups of He-sdOB stars in our samples, which were found by previous studies in the T eff– diagram. Our results demonstrate different origins of field hot subdwarf stars and extreme horizontal branch stars in globular clusters, and provide strict observational limits on the formation and evolution models of the different sub-types of these evolved objects. Based on the results, we evaluated the completeness of the Geier et al. catalog. We found the fraction of hot subwarf stars is between 10% and 60%, depending on the brightness of the sample. A more accurate estimation for the hot subdwarf fraction can be obtained when similar results from composite spectra will become available.

Headspace Oxygen Concentration Measurement for Pharmaceutical Glass Bottles in Open-Path Optical Environment Using TDLAS/WMS

Accurate measurement of oxygen concentration for pharmaceutical glass bottles is of great significance to ensure the asepsis of medicine and stability of ingredients. With merits of high sensitivity, low cost, noncontact, and real-time response, the wavelength-modulation-based tunable diode laser absorption spectroscopy (TDLAS/WMS) technology shows great potential to achieve in-site oxygen concentration detection by the single-line spectrum measurement. This article focuses on headspace oxygen concentration measurement in the open-path optical environment, which is extremely challenging due to the short light path length and random ambient noises. First, a signal reconstruction method is established based on the discrete wavelet packet transform (DWPT), where random noise suppression is implicitly achieved. Then, oxygen concentration is inversed among the data between two adjacent valley values of the demodulated second-harmonic signal by multiple linear regression (MLR), and the linear discriminant analysis (LDA) is imported to enhance the information sparsity of second-harmonic signal matrix and to address the multicollinearity problem. Simulation results prove that our proposed method achieved considerable detection accuracy with the average absolute error of 0.05%. This article also designed a TDLAS/WMS prototype, and the experimental results aiming at glass bottles with different oxygen concentration of 0%, 5%, 10%, and 21% in open-path optical environment indicate our method has achieved an encouraging average absolute error of 0.54% and can survive well when the normalized signal-to-noise ratio (SNR) is within 0.85–1. These results promise that the proposed methodology can be widely applied in in-site automatic optic inspection (AOI) instrumentation of headspace oxygen concentration measurement for glass vials.

A new experimental scheme for nuclear γ-resonance time-domain interferometry.

Time-domain interferometry (TDI) based on nuclear resonant scattering of synchrotron radiation by Mössbauer nuclei is a promising technique to study slow dynamics at the interatomic length scale. In order to improve the efficiency of this technique, a new TDI scheme is developed involving the use of a nuclear absorber with a two-line energy spectrum combined with a single-line spectrum. Different from other TDI setups, the issue of external vibrations is much reduced since the two absorbers are at rest and no velocity transducer is used. This allows measuring beating patterns with satisfying statistical accuracy and contrast up to 350 ns. We report here the characterization of the experimental setup necessary for the implementation of this new scheme. The model required for the description of the beating pattern produced by a three-line spectrum system is also discussed in detail. Finally, we report some results for the dynamics of the prototypical glass-former ortho-terphenyl to demonstrate the possibilities offered by this new scheme.

Redox reactions in a linear polyviologen derivative studied by in situ ESR/UV-vis-NIR spectroelectrochemistry

It is well-known that reductive electropolymerization of cyanopyridinium moieties yields to viologenic materials. In this work, a monomer with two electropolymerizable cyanopyridinium groups separated by a six carbon spacer (CNP) has been synthesized. Its electropolymerization in aqueous electrolyte results in a linear polyviologen (PV) derivative, a purple-colored film deposited on the electrode surface. Cyclic voltammetry (CV) of PV films displays two well-resolved one-electron redox processes at c.a. −0.5 and −1.0 V vs. Ag/AgCl. Fourier transform infrared (FTIR) spectral analysis shows successful polymerization of PV from the CNP monomer. In situ electron spin resonance (ESR)/UV-vis-NIR spectroelectrochemistry was used in order to simultaneously determine the polycation radical as well as the magnetic and optical response of the redox PV system. The single-line ESR spectrum observed at the first reduction peak of PV film was assigned to the formation of stable viologen cation radical species within the polymer matrix, exhibiting the characteristic UV-vis-NIR viologen cation radical absorption bands. The electrosynthesized linear PV system represents a promising stable redox active n-type material for organic rechargeable devices.

Introducing a new azoaromatic pincer ligand. Isolation and characterization of redox events in its ferrous complexes.

The isolation and complete characterization of a new bis-azoaromatic ligand, 2,6-bis(phenylazo)pyridine (L), are described, and its coordination to iron(II) is reported. A pseudo-trigonal-bipyramidal mixed-ligand complex of iron(II), FeLCl2 (1), and a homoleptic octahedral iron complex, mer-[Fe(L)2]ClO4 [2]ClO4, have been synthesized from L and FeCl2 or hydrated Fe(ClO4)2, respectively, in boiling methanol. Determination of the X-ray crystallographic structure together with magnetic data (≈ 5.06 μB) and Mössbauer analysis of 1 established a high-spin Fe(II) complex ligated by one neutral 2,6-bis(phenylazo)pyridine ligand. The X-ray crystallographic structure (showing dN-N > 1.30 Å), Mössbauer data, and magnetic susceptibility measurements (≈ 1.65 μB) as well as a nearly isotropic EPR signal with only a small metal contribution at g = 1.968, on the other hand, suggest a low-spin Fe(II) complex with a one-electron-reduced radical ligand coordination in [2]ClO4. The ligand and the metal complexes have well-behaved redox properties, with the ligand(s) functioning as the redox-active site(s) responsible for redox events. The uncoordinated ligand, L, displays a reversible one-electron wave at -1.07 V and a quasi-reversible wave at -1.39 V. The partially reduced ligand L(•-) shows a single-line EPR spectrum at g = 2.001, signifying that L(•-) is a free radical. While complex 1 shows a reversible reduction at -0.08 V and an irreversible cathodic response at -0.98 V, the bis-chelate [2]ClO4 undergoes a reversible one-electron oxidation at 0.54 V and three successive reversible one-electron reductions at -0.18, -0.88, and -1.2 V, all occurring at the ligands without affecting the metal ion oxidation state. The electronic structures of the parent monocationic complex [2](+) and its oxidized and reduced forms, generated by exhaustive electrolyses, have been characterized by using a host of spectroscopic techniques and density functional theory (DFT). It is found that the 2,6-bis(phenylazo)pyridine ligand (L) is truly redox noninnocent and is capable of coordinating transition-metal centers in its neutral ([L](0)), monoanionic monoradical ([L(•)](-)), and dianionic diradical ([L(••)](2-)) forms.

Fundamental stellar and accretion disc parameters of the eclipsing binary DQ Velorum

To add to the growing collection of well-studied double periodic variables (DPVs) we have carried out the first spectroscopic and photometric analysis of the eclipsing binary DQ Velorum to obtain its main physical stellar and orbital parameters. Combining spectroscopic and photometric observations that cover several orbital cycles allows us to estimate the stellar properties of the binary components and the orbital parameters. We also searched for circumstellar material around the more massive star. We separated DQ Velorum composite spectra and measured radial velocities with an iterative method for double spectroscopic binaries. We obtained the radial velocity curves and calculated the spectroscopic mass ratio. We compared our single-lined spectra with a grid of synthetic spectra and estimated the temperature of the stars. We modeled the V-band light curve with a fitting method based on the simplex algorithm, which includes an accretion disc. To constrain the main stellar parameters we fixed the mass ratio and donor temperature to the values obtained by our spectroscopic analysis. We obtain donor and gainer masses, the radii, and temperatures for the stellar components. We find that DQ Vel is a semi-detached system consisting of a B3V gainer and an A1III donor star plus an extended accretion disc around the gainer. The disc is filling 89% of the gainer Roche lobe and it has a concave shape that is thicker at its edge than at its centre. We find a significant sub-orbital frequency of 0.19 d^{-1} in the residuals of the V-band light curve, which we interpret as a pulsation of an slowly pulsating B-type (SPB) of a gainer star. We also estimate the distance to the binary (3.1 kpc) using the absolute radii, apparent magnitudes, and effective temperatures of the components found in our study.

Ionospheric decontamination for skywave OTH radar based on complex energy detector

For over-the-horizon (OTH) radar, the ocean clutter is very strong. And this becomes a big challenge for the target detection. The clutter suppression is a very important procedure for the OTH radar. For the skywave OTH radar, the radar signal will propagate through the ionosphere. This will cause a contamination due to its unstable movement. Then the Bragg frequencies will be smeared and clutter spectrum will spread wider rather than a single line spectra. This smear will cause the target more difficult to be detected and even buried in clutter. Compensation is necessary to cancel the ionospheric effect. This article proposes the clutter decontamination algorithm based on the complex energy detector (CED). The energy detector (ED) is originally proposed to demodulate the real AM–FM signals. The ED is expanded to complex domain. After the expansion, there is no mutual coupling between the amplitude and frequency component for an AM–FM signal. The phase of the Bragg clutter return contaminated by the ionosphere is modeled by a frequency-modulated signal, while its magnitude is amplitude modulated. The CED algorithm is applied to track the instantaneous frequency of the contaminated return signal, which is then used for compensation. Simulation results are presented. The simulation results show that, comparing with the Hankel rank reduction algorithm, the proposed algorithm has better performance under the situation of large frequency fluctuation.

Charge transfer in the novel donor–acceptor complexes tetra- and hexamethoxypyrene with tetracyanoquinodimethane studied by HAXPES

The effect of charge transfer (CT) in complexes of the donors tetra- and hexamethoxyprene (TMP and HMP) with the classical acceptor tetracyanoquinodimethane (TCNQ) was studied using hard X-ray photoemission (HAXPES). Microcrystals of the complex were grown via vapour diffusion from donor–acceptor mixtures. The bulk sensitivity of HAXPES at a photon energy of 6keV completely eliminates the problem of surface contamination for such delicate organic materials grown from solution. The donor molecules were produced using a novel synthesis route functionalizing polycyclic aromatic hydrocarbons at their periphery. For comparison, spectra were also taken from thin-film samples of the same compounds produced via co-deposition in UHV. Upon complex formation, the oxygen 1s core-level spectra (being a fingerprint of the methoxy-group of the donors) change from the single-line spectrum of pure HMP (TMP) to a spectrum with two distinct lines shifted by 1.4 (0.9)eV and 2.6 (2.3)eV with respect to the position of the oxygen 1s line of the pure donors. The nitrogen 1s spectra (being a fingerprint of the cyano-group in the acceptor) show two peaks as well with a corresponding shift of 0.9eV and 2.0eV in comparison with the leading line of pure TCNQ in opposite direction to the oxygen 1s spectra. These values are substantially larger than shifts in near edge X-ray absorption fine structure (NEXAFS) and ultraviolet photoelectron spectroscopy (UPS) spectra of the same complexes. The changes in the spectra are discussed in terms of the CT in the complexes. Residues of pure donor and acceptor materials in the microcrystal fractions of the complexes are evident from the presence of non-shifted lines. Peak-area analysis reveals that charge is transferred to a fraction of 60% of the molecules in the complexes.

Improvement of Efficiency of Time-Domain Interferometry Method Using Two Driven Nuclear Absorbers

A time-domain interferometry (TDI) method using the nuclear resonant scattering of synchrotron radiation enables us to study the microscopic slow dynamics of around 100 ns in supercooled liquids and soft matters. To improve the TDI efficiency, we developed a new TDI method by adding another driven nuclear absorber with a single-line Mossbauer spectrum to the conventional TDI method. By using the nuclear absorbers with the optimum thickness estimated by simulation, new TDI experiments were successfully performed and the efficiency was improved about two times that obtained by the conventional TDI method used thus far.

Sandwich-type polyoxoanions based on A-β-GeW9 . Synthesis and characterization of [(A-β-GeW9O34)2(MOH2)3CO3]13− (M = Y3+, Sm3+, and Yb3+) polyoxoanions

The title complexes were synthesized at room temperature by the reaction of A-β-GeW9 with MCl3 (M = Y3+, Sm3+, and Yb3+) in 0.1 mol L−1 sodium carbonate solution and characterized by elemental analysis, FT-IR, UV, 13C- and 183W-NMR spectroscopies, and thermogravimetric analysis (TGA). Two-line 183W-NMR spectrum with 2 : 1 intensity ratio confirms that [(A-β-GeW9O34)2(MOH2)3CO3]13− contains an anion of D3h symmetry. The difference of the two chemical shifts Δδ = 30.56 affirms the presence of A-β-GeW9 . The chemical shift of the single-line 13C-NMR spectrum of [(A-β-GeW9O34)2(MOH2)3CO3]13− and frequencies of stretching vibrations of all three complexes affirm the presence of coordinated carbonate. TGA shows that the complexes are thermally stable up to 430°C.

A new EPR dosimeter based on 2:1 mixture of Li 2C 2O 4:Na 2C 2O 4 for gamma and neutron dosimetry

Electron paramagnetic resonance (EPR) investigations of Li 2C 2O 4, Na 2C 2O 4 mixed in proportion 1:0, 0:1, 1:1, 2:1 and 3:1 were carried out to measure the absorbed dose from photons and thermal neutrons in a mixed radiation field. A single line spectrum of CO 2 − radical anion centered around g=2.0045±0.0005 was obtained in the respective cases on gamma and neutron irradiation. Except Na 2C 2O 4, other mixtures had shown increase in line width on neutron irradiation possibly due to relaxation effects. Of all combinations, the 2:1 mixture is the more sensitive material for gamma and thermal neutrons. Intensity of CO 2 − radical signal in 2:1 Li 2C 2O 4:Na 2C 2O 4 mixture was found to be linear from 0.006 to 11 kGy for gamma and 40–1530 kGy for thermal neutron doses. Radical signal was found to be stable over a period of 300 days with marginal fading of less than 1 percent. Experimental results thus obtained suggest 2:1 Li 2C 2O 4:Na 2C 2O 4 mixture as the potential neutron dosimeter for medium and high dose range.

The influence of domains on tetrahedrally coordinatedCr5+ inferroelectric BaTiO3: an electron paramagnetic resonance study

Electron paramagnetic resonance (EPR) spectra of quasi-tetrahedrally coordinatedCr5+ ions(named CrII5+ in contrast to the octahedrally coordinatedCrI5+) in powderedceramic samples of BaTiO3 were investigated in the temperature range 50–220 K at 9.4 and 34.0 GHz(X and Q band). At 50 K, in the ferroelectric low-temperature phasewith rhombohedral symmetry, two peaks in the powder spectrum of the1/2-spinCrII5+ centre show a frequency-dependent doublet splitting which is explained assuming the existence of twoCrII5+ centres withslightly different g tensors. The spontaneous polarization in the ferroelectric domains induces changes in thepeak positions in the spectra and generates alignment effects of the off-centredCr5+ ions.These effects are caused by the linear coupling of the electric dipole moment, associated with the off-centredCr5+ ion within the octahedronof surrounding O2− ions, and the polarization field. At 75 K a dynamic reorientation of the defect ions amongthe possible positions in the unit cell broadens the powder peaks. Above 150 K only anisotropic single-line spectrum is observed, the line width of which increases with risingtemperature.

THE HIGHLY ECCENTRIC PRE-MAIN-SEQUENCE SPECTROSCOPIC BINARY RX J0529.3+1210

The young system RX J0529.3+1210 was initially identified as a single-lined spectroscopic binary. Using high-resolution infrared spectra, acquired with NIRSPEC on Keck II, we measured radial velocities for the secondary. The method of using the infrared regime to convert single-lined spectra into double-lined spectra, and derive the mass ratio for the binary system, has been successfully used for a number of young, low-mass binaries. For RX J0529.3+1210, a long-period (462 days) and highly eccentric (0.88) binary system, we determine the mass ratio to be 0.78 ± 0.05 using the infrared double-lined velocity data alone, and 0.73 ± 0.23 combining visible light and infrared data in a full orbital solution. The large uncertainty in the latter is the result of the sparse sampling in the infrared and the high eccentricity: the stars do not have a large velocity separation during most of their ∼1.3 yr orbit. A mass ratio close to unity, consistent with the high end of the 1σ uncertainty for this mass ratio value, is inconsistent with the lack of a visible light detection of the secondary component. We outline several scenarios for a color difference in the two stars, such as one heavily spotted component, higher-order multiplicity, or a unique evolutionary stage, favoring detection of only the primary star in visible light, even in a mass ratio ∼1 system. However, the evidence points to a lower ratio. Although RX J0529.3+1210 exhibits no excess at near-infrared wavelengths, a small 24 μm excess is detected, consistent with circumbinary dust. The properties of this binary and its membership in λ Ori versus a new nearby stellar moving group at ∼90 pc are discussed. We speculate on the origin of this unusual system and on the impact of such high eccentricity, the largest observed in a pre-main-sequence double-lined system to date, on the potential for planet formation.

Detection of organic free radicals in irradiated Foeniculi fructus by electron spin resonance spectroscopy

Foeniculi fructus were irradiated with an electron beam and organic free radicals were detected by electron spin resonance (ESR) spectroscopy for the purpose of identifying radio-disinfected and sterilized herbal drugs. An ESR single-line spectrum near g = 2.005 was observed in the sample before irradiation. After irradiation, the intensity of the signal near g = 2.005 increased. In addition, two subsignals derived from cellulose radicals were observed approximately 3 mT to either side of the main signal, at g = 2.023 and g = 1.987. The intensity of the subsignal at g = 2.023 was proportional to the absorbed dose of radiation. The decrease in intensity of the signals was considerable 2 weeks after irradiation, and continued to decrease steadily thereafter. Among the signals, the fading of the subsignal at g = 2.023 was relatively small. The intensity of the subsignal at g = 2.023 was detectable for over 1 year in the sample that had been irradiated to the level of disinfection and sterilization. Therefore, organic free radicals in irradiated Foeniculi fructus can be measured rapidly and with high sensitivity by ESR spectroscopy. The stable signal at g = 2.023 is a promising indicator of the detection of irradiated herbal drugs.

Radicals from the Oxidative Pyrolysis of Tobacco

The fractional, oxidative pyrolysis of Bright tobacco was performed in an oxygen/nitrogen atmosphere containing from 0 to 20.4% of O2 over the temperature range of 200–510 °C in a specially constructed, high-temperature flow reactor system. The effect of the temperature and the concentration of oxygen in the reaction atmosphere on the generation of free radicals from Bright tobacco and two major components of Bright tobacco (polyphenols and cell wall biopolymers) were studied. Electron paramagnetic resonance (EPR) spectroscopy was used to analyze for free radicals in the initially produced total particular matter (TPM) and in the gas phase. Two types of radicals were observed in the initially produced TPM: type I radicals characterized by a five-line EPR spectrum with an apparent g-value of ∼2.0064 that was tentatively assigned to a tyrosyl radical formed at lower temperatures from the cell wall biopolymer fraction of tobacco, and type II radicals characterized by a single-line EPR spectrum with g-factor ...