Incident Photon Energy Research Articles

Interface analysis of Mg/Sc and Sc/Mg bilayers using X-ray reflectivity

• Interfaces at the Mg/Sc and Sc/Mg bilayers are investigated. • Bilayers are studied by secondary ion mass spectrometry and x-ray reflectivity. • Mg-on-Sc and Sc-on-Mg interfaces in the bilayers are found to be asymmetric. Mg/Sc and Sc/Mg bilayers were studied to investigate their interfaces. Time-of-flight secondary ion mass spectroscopy and grazing incidence x-ray reflectivity are combined to determine the realistic structure of the bilayer stack: thickness, refractive index, and roughness of layers and interlayers respectively. In addition, soft x-ray reflectivity measurements provide sensitive information about the chemical environment of scandium, when the incident photon energy is tuned in the vicinity of the Sc L-absorption edge (∼ 400 eV). Both Mg-on-Sc and Sc-on-Mg interfaces have high roughness (∼1 nm) and a MgSc compound interlayer but are shown to be asymmetric.

Bandgap tuning and thermoelectric characteristics of Sc-based double halide perovskites K2ScAgZ6 (Z = Cl, Br, I) for solar cells applications

Using the full-potential linearized augmented plane wave plus local orbitals method within the frame work of density functional theory, the Sc-based double halide perovskites K2ScAgZ6 (Z = Cl, Br, I) are investigated for determining their physical properties. To investigate the structural and thermodynamic stability of these Sc-based double halide perovskites we calculate tolerance factor, formation energy, and phonon dispersion curve using GGA-PBEsol approximation. The calculated values of lattice parameters using GGA-PBEsol are found to be consistent with the available data. Subsequently, the Tran-Blaha modified Becke-Johnson (mBJ-LDA) potential is used for electronic properties. Implementation of TB-mBJ potential is clearly shows that K2ScAgZ6 have indirect bandgap, which is consistent with the literature. To evaluate these double perovskites and reveal their potential use in optical devices, several optical parameters are computed for an incident photon energy range of 0–8 eV. The BoltzTraP code is also employed to investigate temperature dependent electrical characteristic of these compounds in the temperature range of 200–600 K. Investigated halide double-perovskites have been shown to display excellent physical properties for solar cells and renewable energy device applications.

Enhancing the radiation absorption ability of the glass system with the contamination of Heavy Metal Oxide (PbO, CuO, and Bi2O3)‏

Containing the molar percentage recipe of 55B2O3–x PbO–(45-x) CuO [ where, x = 5, 10,15, 20, 25 and 30 mol%] glass systems were particularized in this present study. To detect the radiation shielding features such as linear attenuation coefficients (LAC), mass attenuation coefficients (MAC), half value layer (HVL), mean free path (MFP), effective atomic number (Zeff) of these six glasses by using Phy-X software. The obtained results indicate that the value of the studied glass systems represented the highest value of LAC, MAC, and Zeff whereas the lowest value has found for HVL, and MFP. The value of these parameters represented the utmost shielding ability displayed by the studied glass containing the highest mol percentage of the PbO and CuO. Additionally, it has been seen that the density of the glass systems upsurges due to the greater addition of wt% of the PbO and CuO. The studied glass system S6 (30PbO-15CuO-55B2O3) represented a 5.3 times lower value than sample S1(5PbO-40CuO-55B2O3). That means the highest percentage of PbO and CuO enhances the shielding ability. Noteworthy, it has been found from the studied results that with the increase of incident photon energy the value of HVL has increased. Like at energy 1.33 MeV, the half value layer for studied glass sample S1 (5PbO-40CuO-55B2O3) is approximately 3 cm while S6 is 2 cm. In view of the above facts, it can be easily stated that the studied sample S6 (30PbO-15CuO-55B2O3) has the best shielding ability among the six studied glass samples.

Monte Carlo simulation method of polarization effects in Laser Compton Scattering on relativistic electrons

Quasi-monochromatic, high energy and highly polarized γ-ray beam sources based on Compton scattering of laser photons (LCS) on relativistic electrons have developed for the last few decades as established instruments for nuclear physics studies. Following an extensive photoneutron experimental campaign at the LCS γ-ray beam line of the NewSUBARU synchrotron radiation facility at SPring8, Japan, a dedicated simulation code was developed for characterizing the incident γ-ray beams. The eliLaBr code is implemented using Geant4 and is available on the GitHub repository (github.com/dan-mihai-filipescu/eliLaBr). The present work describes step-by-step the Monte Carlo algorithm with focus on modeling the polarization properties of the scattered photon. The polarization is treated independently both in the Stokes parameters and in the polarization vector formalisms. An intervalidation between the two methods is given. Based on polarization state description requirements of different Geant4 physics classes, user recommendations are given on which of the two methods to be employed.The spatial and energy distributions for the LCS γ-ray beam and its Stokes parameters are obtained for head-on laser — relativistic electron collisions, where several incident laser polarization states were considered: linear, unpolarized, circular and mixed linear and circular polarization. Results of previous investigations on the polarization of Compton scattered photons are reproduced.The influence of variable incident angle between photon and electron beam was also investigated. We show that the degree of polarization transfer from the incident photon to the scattered photon increases with the collision angle, where head-on is considered 0°. However, as the polarization transfer is strongly influenced by the incident photon energy, we show that, for γ-ray sources based on Compton scattering of laser photons on relativistic electrons, the polarization degree of the incident photon is almost completely transferred to the scattered photon for any incident angle.

Development of a photoelectron spectrometer for hard x-ray photon diagnostics.

The development and characterization of an angle-resolved photoelectron spectrometer, based on the electron time-of-flight concept, for hard x-ray photon diagnostics at the European Free-Electron Laser, are described. The instrument is meant to provide users and operators with pulse-resolved, non-invasive spectral distribution diagnostics, which in the hard x-ray regime is a challenge due to the poor cross-section and high kinetic energy of photoelectrons for the available target gases. We report on the performances of this instrument as obtained using hard x-rays at the PETRA III synchrotron at DESY in multibunch mode. Results are compared with electron trajectory simulations. We demonstrate a resolving power of 10eV at incident photon energies up to at least 20keV.

Rayleigh scattering from hydrogen atoms including resonances and high photon energies

The nonrelativistic cross section from Rayleigh scattering by hydrogen atoms in the ground state was calculated over a wide range of photon energies (<0.8 keV). Evaluations were performed in terms of the real and imaginary components of the atomic polarizability. The sum over intermediate states that characterizes this second-order radiative process was performed using exact analytic expressions for oscillator strengths of bound and continuum states. Damping terms associated with the finite lifetimes of excited states and their splitting into two fine-structure levels (p1/2 and p3/2) are taken into account in resonance cross sections. Fitting formulas required for cross-section evaluation are presented for incident photon energy (i) redward of the first resonance (Lyman-α1/2), (ii) in the spectral region corresponding to resonances (for an arbitrary number of them), and (iii) above the ionization threshold.

Metal-insulator transition in CuIr2S4 observed by Cu Kα resonant x-ray emission spectroscopy

We have investigated the Cu-derived electronic structure of iridium spinel compound ${\mathrm{CuIr}}_{2}{\mathrm{S}}_{4}$ with a metal-insulator transition (MIT) at ${T}_{\mathrm{MIT}}\ensuremath{\sim}230$ K by means of high-energy resolution fluorescence-detected x-ray absorption spectroscopy (HERFD-XAS) and Cu $K\ensuremath{\alpha}$ resonant x-ray emission spectroscopy (RXES) around the Cu $K$ absorption edge. The Cu $K$ HERFD-XAS spectrum in the metallic phase exhibits a peak in the pre-edge region at an incident photon energy of $h{\ensuremath{\nu}}_{\mathrm{in}}=8981$ eV. The peak is ascribed to the Cu $1s--3d$ quadrupole transition and is abruptly shifted to higher energy by about 0.5 eV on going from metallic to insulating phases. The energy shift of the unoccupied Cu $3d$ states is related to the insulator gap formation of ${\mathrm{CuIr}}_{2}{\mathrm{S}}_{4}$ via the hybridization with the Ir $5d$--S $3p$ bands. A hysteresis behavior is observed in the Cu $1s--3d$ peak intensity between cooling and heating processes around ${T}_{\mathrm{MIT}}$, consistent with those observed in the transport properties. The abrupt change in the unoccupied Cu $3d$ states across MIT is also clearly detected in the Cu $K\ensuremath{\alpha}$ RXES spectra.

A first principle study of pressure‐induced properties of MoS2–graphene heterostructures

AbstractWe examine the capabilities of the ab‐initio calculations within density functional theory (DFT) on the 2D monolayer MoS2, graphene, and Gr‐MoS2 heterostructure. The stability, elastic properties, acoustics, electronic and optical properties of the three hexagonal MoS2, graphene, and Gr‐MoS2 heterostructure is presented. The energy bandgap and both Total and partial density of states are calculated within the PBE functional and are enhanced by the HSE06 functional. Gr‐MoS2 hold an indirect bandgap (0.294 ev) while MoS2 is a direct bandgap (1.83 eV); moreover, graphene is used in its metal form in our calculations. The geometrically optimized relaxed structural parameters are (a = b = 3.308 Å, c = 11.961 Å), (a = b = 3.156 Å, c = 12.440 Å), and (a = b = 2.450 Å, c = 7.286 Å) for Gr‐MoS2, MoS2, and Gr, respectively. The energy bandgap of the three hexagonal crystals is induced in the pressure limit (0–40) GPa. Pressure give rise to bandgap in Gr, and does not affect the MoS2 bandgap significantly, whereas the minimal bandgap for Gr‐MoS2 changes drastically under pressure. The pressure‐dependent elastic moduli and related mechanical characteristics are reported. The optical properties are calculated throughout incident photon energies (0–40 eV). Most of the reported properties show a relative agreement with the cited literature. However, there are no experimental nor reliable theoretical results for the Gr‐MoS2 heterostructure, and to the best of the author's knowledge many of the results of Gr‐MoS2 are reported first in this work.

Development of an MPPC-based gamma-ray detector onboard a radiation source imager under high-dose environments and initial performance results

Since the accident at the Fukushima Daiichi Nuclear Power Plant ∼10 years ago, various studies have been conducted focusing on the decontamination of radioactive materials and the decommissioning of the remains of the reactor. It is crucial to identify the locations of radioactive materials for the decontamination of a building that is exposed to high radiation doses. One of the most widely used methods is the visualization of gamma rays with energy information using a photon-counting imager. However, the existing imagers have limited functionality, making it difficult to implement them in such an environment. Therefore, we have developed a novel pinhole gamma imager containing multi-pixel photon counters (MPPCs) combined with fast scintillators, which are processed using fast signal-processing analog and digital large integrated circuits under high-dose environments. The two-dimensional sensor array developed in this study can obtain incident gamma-ray photon energies with a counting rate of a few MHz/mm2. Furthermore, we were able to perform two-dimensional gamma-ray imaging of an extremely strong radiation source of 60Co with ∼45 TBq, by combining the sensor array with the dedicated tungsten collimator and housing.

First-principles calculations to investigate structural, elastic, optical, and thermoelectric properties of narrow band gap semiconducting cubic ternary fluoroperovskites barium based BaMF3 (M = Ag and Cu) compounds

Herein the first-principle modeling within the DFT framework is used to investigate the structural, optoelectronic, elastic, and thermoelectric properties of BaMF3 (M = Ag and Cu) ternary halide Perovskites compounds. The computed tolerance factors for BaAgF3 and BaCuF3 are 0.919 and 0.991 respectively, indicating that the cubic crystal phase of these selected compounds is thermodynamically and mechanically stable. It is found that both the compounds are structurally stable according to the Birch-Murnaghan fit curve for optimization. The IRelast package is used for investigating the elastic properties of both cubic compounds and the findings show that these compounds are mechanically stable, scratch-resistant, ductile, anisotropic, and resistant to plastic deformation. The Trans-Blaha modified Becke-Johnson (TB-mBJ) approximation is employed to determine electronic properties with accuracy and precision. The electronic-band structure analysis depicts a narrow band gap semiconductor nature of BaAgF3 and BaCuF3 compounds which displays indirect band gaps of 0.2 eV for BaAgF3 and 0.3 eV for BaCuF3 at the high symmetrical points from (Γ–M). Furthermore, the computations of total densities of states (TDOS) and partial densities of states (PDOS) are carried out to determine how different states contribute to the various band structures. The optical characteristics of BaAgF3 and BaCuF3 are comprehensively examined in 0–40 eV energy ranges. The selected materials possess high optical conduction and absorption coefficients at the high level of photon energies and show transparency at low incident photon energy ranges. The investigations of optical properties led us to the conclusion that BaAgF3 and BaCuF3 are suitable to use in high-frequency UV devices. The thermoelectric properties show that both materials hold high-power factors, electrical conductivity, and figures of merit (ZT), indicating that they are good thermoelectric materials. This is the first theoretical computational systematic analysis of structural, optoelectronic, elastic, and thermoelectric properties of BaMF3 (M = Ag and Cu) that will be experimentally validated to our knowledge.

The total absorption coefficient and refractive index change of a spherical quantum dot in the confinement radial potential

We have systematically investigated the linear, third-order nonlinear, total absorption coefficients and refractive index change of the spherical quantum dot in the confinement potential family V(r)=Ar2−Br+Crκ by solving the radial Schrödinger equation with the Numerov method in case of the effective mass approximation for the allowed transition of the ground state (1s) to first excited state (2p). We examine the dependencies of the total absorption coefficient and refractive index change on the confinement potential parameters for varying incident photon energy and relaxation times. Our results demonstrate that the absorption coefficients and the change in refractive index strongly depend on the confining potential parameters non-linearly representing various intersubband transitions of quantum dots. We find that increasing the parameter B in the Coulomb plus harmonic oscillator potential or decreasing the parameter A in the Kratzer plus harmonic oscillator potential, the total absorption coefficient and refractive index change shift to higher photon energies.

In situ work function measurements of W, WO3 nanostructured surfaces

Surface nanostructuring enables the fabrication of materials with highly desirable properties. Nanostructured tungsten surfaces have potential applications in solar water splitting. Exposing a polished tungsten surface to helium plasma induces various surface morphological changes. Depending on the helium ion energy, temperature, and fluence, helium clusters, helium bubbles and foam-like nanostructures develop on the tungsten surface. In this study, tungsten foam-like nanostructures were formed and/or oxidised, and then examined using X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) without breaking the vacuum. The chemical state of nanostructured W or WO3 was not modified in comparison to the pristine one. However, measuring the line width of the emitted electrons from the onset of the secondary electrons up to the Fermi edge and subtracting value from the incident photon energy, the work function acquired in situ by UPS for a nanostructured W surface increased by 0.9 eV in comparison to the pristine one. Helium ions effectively eliminated field emission sites via sputtering/implantation and thereby increased the work function. No change in work function was measured for WO3-pristine and its fuzz: the oxidation hindered the effect of helium. In contrast to the W-fuzz sample, no helium bubbles were identified in WO3-fuzz, as helium diffused out during oxidation.

Indirect x-ray photodesorption of N215 and CO13 from mixed and layered ices

X-ray photodesorption yields of N215 and CO13 are derived as a function of the incident photon energy near the N (∼400 eV) and O K-edge (∼500 eV) for pure N215 ice and mixed CO13:N215 ices. The photodesorption spectra from the mixed ices reveal an indirect desorption mechanism for which the desorption of N215 and CO13 is triggered by the photoabsorption of CO13 and N215, respectively. This mechanism is confirmed by the x-ray photodesorption of CO13 from a layered CO13/N215 ice irradiated at 401 eV on the N 1s → π* transition of N215. This latter experiment enables us to quantify the relevant depth involved in the indirect desorption process, which is found to be 30–40 monolayers in that case. This value is further related to the energy transport of Auger electrons emitted from the photoabsorbing N215 molecules that scatter toward the ice surface, inducing the desorption of CO13. The photodesorption yields corrected from the energy that can participate in the desorption process (expressed in molecules desorbed by eV deposited) do not depend on the photon energy; hence, they depend neither on the photoabsorbing molecule nor on its state after Auger decay. This demonstrates that x-ray induced electron stimulated desorption, mediated by Auger scattering, is the dominant process explaining the desorption of N215 and CO13 from the ices studied in this work.

TeO2 for enhancing structural, mechanical, optical, gamma and neutron radiation shielding performance of bismuth borosilicate glasses

The synthesized 12Bi2O3– 8BaO–12ZnO-0.5CeO2-17.5SiO2- (50-x) B2O3- xTeO2 glasses with x = 0, 10, 20, 30 and 40 mol% (coded BiTe-0 to BiTe-40) were investigated in terms of physical, structural, optical and mechanical properties to examine the influence of CeO2 and TeO2 on the heavy metal oxide (HMO) borosilicate network. Density values increased continuously with increasing TeO2 concentration with BiTe-40 glass exhibiting maximum value of 5.0875 gcm−3. This property helped in enhancement of refractive index values from 1.769 for BiTe-0 to 1.942 for BiTe-40. Fourier transform infrared (FTIR) analysis of studied glasses revealed the presence of additional small peak at 683 cm−1 in BiTe-30 and BiTe-40 which confirmed the formation of stable TeO4 units in the glass network. The deep brown colour of the glass existing due to bismuth's presence was nullified by CeO2 and TeO2 additives which improved transparency of the glass. Urbach analysis of these glasses led to optical bandgap variation between 3.27 eV and 2.73 eV for 0–40 mol% TeO2 concentration. Makishima and Mackenzie model was utilized for evaluation of elastic property of the glasses, and Poisson's ratio ranging between 1.935 and 1.953 was obtained. Vickers micro-indentation test on the current glasses revealed decreasing microhardness from 4.116 to 4.076 GPa with TeO2 variation from 0 to 40 mol% at 9.8 N load. Gamma radiation shielding parameters were determined using Phy-X/PSD software and it was found that BiTe-40 glass produce maximum MAC (mass attenuation co-efficient) values in high photon energy region 3.5–15 MeV. The present article also contains a detailed emphasis on behaviour of gamma radiation build-up factors at different incident photon energy and TeO2 concentration. The increasing trend of exposure build up factor (EBF) was seen with increasing penetration depth inside the samples at all energies, indicating that glasses of larger thickness improve the escape probability of photons. Meanwhile, fast neutron removal cross-section (FNRCS) was highest for BiTe-10 sample (0.10118 cm−1) which also surpassed the value of ordinary concrete (0.093 cm−1). Overall, the present glass system bested other conventional shields available commercially in terms of gamma and neutron radiation shielding effectiveness.

Nonlinear optical absorption of Co3(PO4)2·4H2O nanosheets in broadband spectra

Long hexagonal Co3(PO4)2·4H2O nanosheets were synthesized using a hydrothermal method, where their nonlinearity was probed via a femtosecond Z-scan system. The results show that the Co3(PO4)2·4H2O nanosheets exhibit saturable absorption when the incident photon energy is greater than the forbidden band width, while optical limiting is found when the incident photon energy is smaller than the forbidden band width. In particular, the obtained Co3(PO4)2·4H2O nanosheets demonstrate the best optical limiting properties at 600 nm. The present study suggests the cobalt phosphates nanosheets as a promising candidate for optical limiters.

Simulation of Mushroom Nanostructures with Ag Nanoparticles for Broadband and Wide-Angle Superabsorption

Metal nanoparticles (NPs) concentrate the energy of incident photons through plasmon resonance excitation, which allows scattering into a substrate with a high refractive index, and the radiated energy from this excitation significantly increases the optical absorption of the substrate. In this work, the effect of Ag NPs on the absorption capacity of mushroom-nanostructured Si metasurfaces was analyzed using the finite-difference time-domain method. It was observed that the absorbance in the metasurfaces with Ag NPs increased from 90.8% to 98.7% compared with nanostructured Si metasurface without NPs. It was shown that the plasmon resonance effect of Ag NPs enlarged the range of the FP cavity by about 10 times, and the electric field strength E2 increased by about four times through the combination of Ag NP and Si absorbers. Meanwhile, the effect of randomly distributed nanostructures on the absorption properties of Si metasurfaces was simulated. Additionally, the nanostructured surface with Ag NPs was insensitive to angle, which encourages the design of broadband and wide-angle superabsorption nanostructures.

Engineering the band gap and optical properties of a two-dimensional molybdenum carbon fluoride MXene

Using first-principles density functional theory, we investigated the electronic and optical properties of monolayer and multilayer nanosheets of molybdenum carbon fluoride (Mo2CF2), a two-dimensional (2D) transition-metal carbide MXene. The indirect band gap of the Mo2CF2 semiconductor can be engineered by controlling the number of layers where the band gap energy changes from 0.278 eV for the monolayer to 0.249 eV for the trilayer nanosheet. The decrease in band gap energy in the multilayer is due to interlayer coupling, which splits the bands according to the number of layers. Mo2CF2 behaves as a metal with an anomalous dispersion and high optical conductivity at incident photon energies of 0.68–2.19, 3.49–6.68 and 7.30–8.31 eV. It has a relatively low reflectivity and is absorbing over a broad range of photon energies from about 0.429 (2890), 0.387 (3204) and 0.345 eV (3594 nm) for the monolayer, bilayer and trilayer nanosheets, respectively, achieving peak absorption in the vacuum ultraviolet region at about 7.9 eV (157 nm). The optical properties of Mo2CF2 can likewise be tuned by varying the number of layers. The unique behavior of its optical properties along with the ability to control its electronic and optical properties enhances the potential of 2D Mo2CF2 for various applications in the fields of electronics and energy storage.

1,1,1,2-tetrafluoroethane photofragmentation: a translational kinetic energy release analysis in the EUV and X-ray energies range

A molecule with two or more atoms of the same element in distinct chemical environments is a trial system for probing site-specific fragmentation. In this context, special attention is deserved to 1,1,1,2-tetrafluoroethane (CF3CH2F), which has been the subject of numerous studies. This work discusses the effects of extreme ultraviolet (EUV) and soft X-ray irradiation on CF3CH2F from a dedicated translational kinetic energy release (KER) perspective. This analysis is achieved by evaluating the mean KER for its fragments at photon energies over 30–320 eV and computing the KER distribution (KERD) for the main fragments over the 282–320 eV range. The questions of interest from the point of view of the present study are twofold: (i) How do the mean KER of ionic fragments of the valence or core-excited CF3CH2F molecule change as a function of incident photon energy? (ii) Is there any evidence of site-specific or state-specific dissociation mechanisms in a molecule containing two carbon atoms in distinct chemical environments? From our results, lighter fragments showed to have their mean KER virtually following respective ion yields previously reported. And the overall learning is that the chemical environment associated with each C 1s excitation plays a role in differentiating the KER results.

Excited-state exchange interaction in NiO determined by high-resolution resonant inelastic x-ray scattering at the Ni M2,3 edges

The electronic and magnetic excitations of bulk NiO have been determined using the ${}^{3}{A}_{2g}$ to ${}^{3}{T}_{2g}$ crystal-field transition at the Ni ${M}_{2,3}$ edges with resonant inelastic x-ray scattering at 66.3- and 67.9-eV photon energies and 33-meV spectral resolution. Unambiguous assignment of the high-energy side of this state to a spin-flip satellite is achieved. We extract an effective exchange field of $89\ifmmode\pm\else\textpm\fi{}4$ meV in the ${}^{3}{T}_{2g}$ excited final state from empirical two-peak spin-flip model. The experimental data is found consistent with crystal-field model calculations using exchange fields of 60--100 meV. Full agreement with crystal-field multiplet calculations is achieved for the incident photon energy dependence of line shapes. The lower exchange parameter in the excited state as compared to the ground-state value of 120 meV is discussed in terms of the modification of the orbital occupancy (electronic effects) and of the structural dynamics: (A) With pure electronic effects, the lower exchange energy is attributed to the reduction in effective hopping integral. (B) With no electronic effects, we use the $S=1$ Heisenberg model of antiferromagnetism to derive a second-nearest-neighbor exchange constant ${J}_{2}$ = $14.8\ifmmode\pm\else\textpm\fi{}0.6$ meV. Based on the linear correlation between ${J}_{2}$ and the lattice parameter from pressure-dependent experiments, an upper limit of 2% local Ni-O bond elongation during the femtosecond scattering duration is derived.

An accurate probabilistic model with detector resolution and Doppler broadening correction in list-mode MLEM reconstruction for Compton camera

Objective. The Compton cameras have been researched for medical applications and radioactive material detection. It is challenging for the Compton camera to realize high-resolution reconstruction when the incident photon energy is below 200 keV. However, multiple kinds of nuclear medical radionuclides are in this energy range, such as 201Tl, 67Ga, 99mTc, and 123I. In this work, we propose an improved probabilistic model with correction of detector energy resolution, detector spatial resolution, and Doppler broadening effect. The proposed model is used for numerical calculation of the system matrix in the list-mode maximum likelihood expectation maximization (LM-MLEM) algorithm. Approach. The model can improve the imaging resolution of LM-MLEM reconstruction by taking Doppler broadening effect into account. It performs well, especially in the following situations: low-energy photon incidence below 200 keV or (and) small distance between scattering and absorbing positions. Main results. Firstly, three main factors that affect the angular resolution of the Compton camera are theoretically analyzed and quantitatively calculated. The results of the analysis indicate the necessity of including the Doppler broadening effect in the model. Secondly, the details and derivation of the proposed probabilistic model are described. Thirdly, both Monte Carlo (MC) simulations and experiments are carried out to verify the performance of the proposed algorithm. The simulations focus on the low-energy reconstruction in which 201Tl (70 keV) and 99mTc (141 keV) are simulated. And the experiments are based on a single-layer Compton camera composed of a Timepix3 detector. Significance. The results of the simulations and the Timepix3-based experiments are presented to verify the effectiveness of the proposed algorithm. The model improves the Compton imaging resolution when the photon energy is below 200 keV.