Rate Equations Research Articles

Experimental study on rotational energy transfer in LiH (X1Σ+ v) + Ar collisions

Abstract Using high-resolution transient laser spectroscopy, the rotational energy transfer between LiH (12, 8) and Ar through collisions was studied. LiH (12, 8) was generated via degenerate stimulated hyper-Raman (DSHR) scattering. The population of LiH (12, J″ ≠ 8) generated during collisions were obtained using transient laser-induced fluorescence (LIF). According to the rate equation, the rate coefficients for the transfer from (12, 8) to (12, J″) states are between 7.1×10-12 and 3.5×10-13 cm3 molecule-1 s-1 within 2 μs of the collision occurring. Above 2 μs, the rate coefficient is no longer constant. Meanwhile, no vibrational relaxation occurs before 10 μs. The rotational energy Erot is the sum of the rotational energies of rotational states (12, J″). Within the period of 0-10 μs, the value of Erot decreases from 541 cm-1 to 390 cm-1. The distribution of translational energy Etrans at different moments of LiH (12, 8) is obtained by measuring the Doppler broadened line widths. It increases from 707 cm-1 at 0 μs to 852 cm-1 at 10 μs. Therefore, when rotational relaxation occurs, the decrease in rotational energy is approximately equal to the increase in translational energy.

High-power idler-resonant intracavity KTA OPO driven by a dual-loss-modulated Q-switched mode-locked laser with AOM and Sb2Te3 nanosheets

By using Sb2Te3 nanosheets as saturable absorbers (SA) and an acousto-optic modulator (AOM), a laser-diode (LD) end-pumped idler-resonant KTiOAsO4 (KTA)-based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss-modulated Q-switched mode-locked (QML) laser has been realized. The experimental results show that the pulse widths of the Q-switched envelope and the mode-locking pulse numbers underneath the Q-switched envelope decrease as the pump power increases. When the pump power reaches a certain value, only one mode-locking pulse underneath a Q-switched envelope exists, resulting in the generation of the subnanosecond mode-locking pulses of OPO with the repetition rate of AOM. The minimum mode-locking pulse durations of the signal and idler waves were measured to be 545 and 936 ps at an AOM frequency of 1 kHz and a diode pump power of 22.45 W, corresponding to the maximum peak powers of 648 and 185 kW, respectively. Furthermore, a set of coupled rate equations for the dual-loss-modulated QML laser-pumped intracavity idler-resonant OPO was formulated according to the Gauss distribution of intracavity photon density. The numerical simulations of these equations agree with the experimental results. These results collectively suggest the potential application of Sb2Te3 as a promising nanomaterial in the realm of optoelectronics.

The degradation of 8 PPCPs in UV/chlorine: Effect of chloride and sulfate ions and the role of radicals

The degradation of 8 structurally diverse pharmaceuticals and personal care products (PPCPs) by UV/chlorine and the effects of Cl- and SO42- were systematically investigated. The 8 PPCPs are divided into 2 groups based on their stability under UV light. This is the first time the kinetic degradation of the 8 PPCPs in the presence of Cl- and SO42- have been intensively evaluated. The results showed that the high degradation rate of the PPCPs is attributed to their second-order rate constants towards radicals (i.e., •OH, and reactive chlorine species (RCS)). 0 - 500mM Cl- enhanced kPPCPs, while this range of SO42- inhibited most of them (except in the case of ciprofloxacin (CIP)). An overview of the effect of 0 – 200mM Cl-/SO42- on the degradation of micropollutants by different UV-based advanced oxidation processes (UV-AOPs) in previous studies indicates that Cl-/SO42- can cause varying effects on the degradation rate of pollutants (i.e., “increase”, “decrease”, or “no effect”), depending on the type of pollutant and the process. Cl-/SO42- did not change the trend of pH influence on the PPCPs degradation rates by UV/chlorine. Acidic and neutral conditions were favorable to the degradation of the PPCPs in all cases. Under three operating conditions (i.e., the control process, 500mM Cl- and SO42-), [•OH]ss decreased considerably, but [Cl•]ss or ([Cl•]ss + [SO4•-]ss) slightly fluctuated when the pH was increased from 2.5 to 10.5. The synergistic effect of seawater and Cl-/SO42- significantly improved some kPPCPs, thereby, decreasing energy consumption.

Modelling co-evolution of resource feedback and social network dynamics in human-environmental systems

Games with environmental feedback have become a crucial area of study across various scientific domains, modelling the dynamic interplay between human decisions and environmental changes, and highlighting the consequences of our choices on natural resources and biodiversity. In this work, we propose a co-evolutionary model for human-environment systems that incorporates the effects of knowledge feedback and social interaction on the sustainability of common pool resources (CPRs). The model represents consumers as agents who adjust their resource extraction based on the resource’s state. These agents are connected through social networks, where links symbolize either affinity or aversion among them. The interplay between social dynamics and resource dynamics is explored, with the system’s evolution analyzed across various network topologies and initial conditions. We find that knowledge feedback can independently sustain CPRs. However, the impact of social interactions on sustainability is dual-faceted: it can either support or impede sustainability, influenced by the network’s connectivity and heterogeneity. A notable finding is the identification of a critical network mean degree, beyond which a depletion/repletion transition parallels an absorbing/active state transition in social dynamics, i.e. individual agents and their connections are/are not prone to being frozen in their social states. Furthermore, the study examines the evolution of the social network, revealing the emergence of two polarized groups where agents within each community have the same affinity. Finally, we observe an inverse relationship between system complexity and sustainability. Comparative analyses using Monte–Carlo simulations and rate equations are employed, along with analytical arguments, to reinforce the study’s findings. The model successfully captures key aspects of the human-environment system, offering valuable insights to understand how both the spread of information and social dynamics may impact the sustainability of CPRs.

Peroxynitrite: A tale of two radicals

The published syntheses of peroxynitrite from azide, nitrite, amylnitrite, hydroxylamine, nitrogen monoxide, and ammonia are discussed. With one exception, all of these syntheses yield peroxynitrite contaminated with nitrate and nitrite as well as reactants. The rate constant for the reaction of nitrogen monoxide with superoxide has been determined by pulse radiolysis and flash photolysis. In pulse radiolysis studies, the formation of the reactants may be rate-limiting and could lead to underestimation of the second-order rate constant. The conditions of flash photolysis experiments can be chosen to minimize conflict between reactant formation and the reaction half-life, thus the rate constant of 1.6 × 1010 M−1s−1 determined by flash photolysis is preferred. The toxicity of peroxynitrite can be attributed mainly to its rapid reaction with carbon dioxide to yield the oxidizing trioxidocarbonate(•1−) and nitrogen dioxide radicals.

Description of step loads at high temperature creep of metallic materials

Abstract In metallic materials under high-temperature creep conditions, the damage evolution occurs. To describe it, Kachanov and Rabotnov proposed the concept of damage. In this paper, the damage parameter is defined as the relative change in material density, serving as an integral measure of damage. By incorporating the damage parameter and the mass conservation law, are we formulated interrelated kinetic equations for rate of creep deformation and the damage parameter. The case of variable loads is crucial both theoretically and practically, as most structural components typically operate under such conditions. Therefore, solutions of considered equations are derived for the case of two-stage loading. The received solutions and experimental results on the creep of titanium alloy under variable loads at 500°C were compared. There is a good agreement between the theoretical results and experimental data.

Ferrous iron oxidation efficiency and kinetics by indigenous iron-oxidizing bacteria in acid mine drainage

Biological Fe(II) oxidation by iron-oxidising bacteria (FeOBs) at low pH is a cost-effective treatment for acid mine drainage (AMD). However, treatments based on this process are limited because of uncertainties regarding the ability and rate of oxidation of Fe(II) from AMD. In the present study, an indigenous FeOBs consortium was enriched in AMD, and its ability to oxidise Fe(II) is described. The bio-oxidation rate of Fe(II) was 39.1mg/(L·h) under optimal culture conditions [35 ℃, pH 2.0, 500mg/L Fe(II)]. In addition, the oxidation rate equation of Fe(II) could be fitted to a zero-order kinetic model, indicating that Fe(II) was oxidised at a constant rate. Furthermore, a continuous-flow bioreactor was developed to simulate the Fe(II) oxidation efficiency of indigenous FeOBs for in situ AMD biological treatment. The maximum Fe(II) oxidation rate was 22.8mg/(L·h) when the influent Fe(II) load was 32.3mg/(L·h). Acidithiobacillus and Acidiphilium were the dominant species contributing to Fe(II) oxidation in the bioreactor, accounting for 67.7% and 32.8%, respectively. The results will help promote the application of FeOBs in AMD treatment.

A comparative study on the oxidation behaviour of NbC-Ni, WC-Co, and high entropy carbide-Ni based cermets

The oxidation behaviour of NbC-13.5(wt%)Ni, NbC-5.7Mo2C-13.3Ni and WC-12Co was compared to that of equimolar quinary (Ti0.2V0.2Nb0.2Ta0.2W0.2)C-10Ni and non-equimolar senary (Ti0.2V0.2Nb0.2Ta0.2Mo0.1W0.1)C-10Ni high entropy carbide (HEC)-Ni cermets. Isothermal oxidation experiments were performed at 700 °C, whereas non-isothermal calorimetric experiments were conducted to determine the onset temperature of oxidation. HEC-based cermets exhibited superior oxidation resistance and a unique oxide layer morphology, which was attributed to the formation of a chemically complex oxide scale mainly consisting of (Ti,V,Nb,Ta,Ni)Ox and Ni(Mo,W)O4. The NbC-based cermets showed the least oxidation resistance and formed a porous oxide layer of Nb2O5 and (Nb,Ni)Ox, whereas WC-Co showed an intermediate oxidation behaviour with respect to the HEC-Ni based cermets. All composites followed a linear oxidation rate law, and the senary HEC cermet demonstrated the slowest oxidation kinetics.

Modeling on multi-level rate equation and rovibrational relaxations of HBr-filled hollow-core fiber lasers

Modeling on multi-level rate equation and rovibrational relaxations of HBr-filled hollow-core fiber lasers

Analysis of a Resistive-Capacitive Shunted Josephson Junction with Topologically Nontrivial Barrier Coupledto a RLC Resonator

This paper presents the resistive-capacitive shunted Josephson junction (RCSJJ) with a topologically nontrivial barrier (TNB) coupled to a linear RLC resonator. The rate equations describing RCSJJ with TNB coupled to the linear RLC resonator are established via Kirchhoff’s current and voltage laws. The model exhibits four, two, or no equilibrium points depending on the external direct current (DC) source and the fractional parameter. The stability analysis of the equilibrium points with credit to the Routh-Hurwitz stability criterion reveals that the stability of equilibrium points depends on the DC source and the fractional parameter. Current-voltage characteristic reveals the presence of a birhythmicity zone which is sensitive to the fractional parameter m. As the fractional parameter increases, the coexistence of the resonant state is destroyed, which is followed simultaneously by the appearance of a new resonance state. Depending on initial conditions, birhythmic behaviour is characterized by the existence of a limit cycle. The projection of the phase space in the specific plane and the time evolution of charge is predicted in which the amplitude of attractors reported is sensitive to the parameter m. Lastly, with a defined fractional parameter, the amplitude of the branch locked to the resonator is greater than the unlocked branch.

Molecular Basis of Influence of A501X Mutations in Penicillin-Binding Protein 2 of Neisseria gonorrhoeae Strain 35/02 on Ceftriaxone Resistance

The increase in the resistance of mutant strains of Neisseria gonorrhoeae to the antibiotic ceftriaxone is pronounced in the decrease in the second-order acylation rate constant, k2/KS, by penicillin-binding protein 2 (PBP2). These changes can be caused by both the decrease in the acylation rate constant, k2, and the weakening of the binding affinity, i.e., an increase in the substrate constant, KS. A501X mutations in PBP2 affect second-order acylation rate constants. The PBP2A501V variant exhibits a higher k2/KS value, whereas for PBP2A501R and PBP2A501P variants, these values are lower. We performed molecular dynamic simulations with both classical and QM/MM potentials to model both acylation energy profiles and conformational dynamics of four PBP2 variants to explain the origin of k2/KS changes. The acylation reaction occurs in two elementary steps, specifically, a nucleophilic attack by the oxygen atom of the Ser310 residue and C–N bond cleavage in the β-lactam ring accompanied by the elimination of the leaving group of ceftriaxone. The energy barrier of the first step increases for PBP2 variants with a decrease in the observed k2/KS value. Submicrosecond classic molecular dynamic trajectories with subsequent cluster analysis reveal that the conformation of the β3–β4 loop switches from open to closed and its flexibility decreases for PBP2 variants with a lower k2/KS value. Thus, the experimentally observed decrease in the k2/KS in A501X variants of PBP2 occurs due to both the decrease in the acylation rate constant, k2, and the increase in KS.

A theory of phonon-induced friction on molecular adsorbates

In this manuscript, we provide a general theory for how surface phonons couple to molecular adsorbates. Our theory maps the extended dynamics of a surface's atomic vibrational motions to a generalized Langevin equation, and by doing so captures these dynamics in a single quantity: the non-Markovian friction. The different frequency components of this friction are the phonon modes of the surface slab weighted by their coupling to the adsorbate degrees of freedom. Using this formalism, we demonstrate that physisorbed species couple primarily to acoustic phonons while chemisorbed species couple to dispersionless local vibrations. We subsequently derive equations for phonon-adjusted reaction rates using transition state theory and demonstrate that these corrections improve agreement with experimental results for CO desorption rates from Pt(111).

A Mechanistic Study on Iron-Based Styrene Aziridination: Understanding Epoxidation via Nitrene Hydrolysis

Transition-metal-catalyzed nitrene transfer reactions are typically performed in organic solvents under inert and anhydrous conditions due to the involved air and water-sensitive nature of reactive intermediates. Overall, this study provides insights into the iron-based ([FeII(PBI)3](CF3SO3)2 (1), where PBI = 2-(2-pyridyl)benzimidazole), catalytic and stoichiometric aziridination of styrenes using PhINTs ([(N-tosylimino)iodo]benzene), highlighting the importance of reaction conditions including the effects of the solvent, co-ligands (para-substituted pyridines), and substrate substituents on the product yields, selectivity, and reaction kinetics. The aziridination reactions with 1/PhINTs showed higher conversion than epoxidation with 1/PhIO (iodosobenzene). However, the reaction with PhINTs was less selective and yielded more products, including styrene oxide, benzaldehyde, and 2-phenyl-1-tosylaziridine. Therefore, the main aim of this study was to investigate the potential role of water in the formation of oxygen-containing by-products during radical-type nitrene transfer catalysis. During the catalytic tests, a lower yield was obtained in a protic solvent (trifluoroethanol) than in acetonitrile. In the case of the catalytic oxidation of para-substituted styrenes containing electron-donating groups, higher yield, TON, and TOF were achieved than those with electron-withdrawing groups. Pseudo-first-order kinetics were observed for the stoichiometric oxidation, and the second-order rate constants (k2 = 7.16 × 10−3 M−1 s−1 in MeCN, 2.58 × 10−3 M−1 s−1 in CF3CH2OH) of the reaction were determined. The linear free energy relationships between the relative reaction rates (logkrel) and the total substituent effect (TE, 4R-PhCHCH2) parameters with slopes of 1.48 (MeCN) and 1.89 (CF3CH2OH) suggest that the stoichiometric aziridination of styrenes can be described through the formation of a radical intermediate in the rate-determining step. Styrene oxide formation during aqueous styrene aziridination most likely results from oxygen atom transfer via in situ iron oxo/oxyl radical complexes, which are formed through the hydrolysis of [FeIII(N•Ts)] under experimental conditions.

Investigating the synergetic effect of tungsten oxide doping into the 1,3-dicarbonyl moiety grafted chitosan and phytic acid impregnated sodium alginate for efficient U(VI) adsorption

In this work, chemical modification of the chitosan with ethyl acetoacetate was performed through a base-catalyzed reaction in which epichlorohydrin facilitated the insertion as well as nucleophilic substitution reaction to graft the 1,3-dioxo moiety across the linear chains of the base biopolymer to establish specificity and selectivity for U(VI) removal. The modified chitosan (EAA-CS) was intercalated into phosphate rich alginate matrix (PASA). Later on, the WO3-doped composites with different WO3 to PASA mass ratio were prepared and characterized using FTIR, XPS, SEM-EDS, XRD, and elemental mapping analysis. WO3 significantly contributed to chemically stable inorganic-organic composites with improved porous texture. Among the prepared composites, MCPS-3 microspherical beads, having mass ratio of 30.0 % w/w, exhibited excellent sorption capacity for U(VI) at an optimal pH 4.5. The successful U(VI) sorption was validated by the existence of two U4f peaks at 392.25 and 381.36 eV due to U4f5/2 and U4f7/2 sub-peaks with an intensity ratio of 3:4, respectively. Batch mode sorption kinetics followed pseudo-second-order rate equation (R2 ≈ 0.99, qe,th ≈ 116.88 mg/g, k2 = 0.86 × 10−4 g/mg.min−1) and equilibrium sorption data aligns with Langmuir (R2 = 0.99, qm = 343.85 mg/g at 310 K and pH = 4.5, KL = 2.00 × 10−2 L/mg) and Temkin models (R2 ≈ 0.99). Thermodynamic parameters ΔHo (30.51 kJ/mol), ΔSo (0.19 kJ/mol.K) and ΔGo (−25.64, −26.89, and − 27.91 kJ/mol) at 298, 305, and 310 K, respectively, suggested that the uptake process is feasible, endothermic and spontaneous. Based on these findings, it is reasonable to conclude that MCPS-3 could be a better hydrogel-based biomaterial for appreciable uranium recovery.

Interaction of exotic states in a hadronic medium: the Zc (3900) case

Abstract We investigate the interactions of the charged exotic state $Z_c(3900)$ in a hadronic medium composed of light mesons. We study processes such as $Z_c \pi \to D\bar{D}$, $Z_c \pi \to D^*\bar{D}^*$, $Z_c \pi \to D\bar{D}^*$ and the inverse ones. Using effective Lagrangians and form factors calculated with QCD sum rules (treating the $Z_c(3900)$ as a tetraquark) we estimate the vacuum and thermally-averaged cross-sections of these reactions. We find that the $Z_c(3900)$ has relatively large interaction cross sections with the constituent particles of the hadronic medium.
After that, we use the production and suppression cross sections in a rate equation to estimate the time evolution of the $Z_c$ multiplicity. We include the $Z_c$ decay and regeneration terms. The coalescence model is employed to compute the initial $Z_c$ multiplicity for the compact tetraquark configuration. Our results indicate that the combined effects of hadronic interactions, hydrodynamical expansion, decay and regeneration affect the final yield, which is bigger than the initial value. Besides, the dependence of the $Z_c$ final yield with the centrality, center-of-mass energy and the charged hadron multiplicity measured at midrapidity $[dN_{ch}/d\eta \,(\eta<0.5)]$ is also investigated.

Silica-Reinforced AMP-Calcium Alginate Beads for Efficient and Selective Removal of Cesium from a Strong Acidic Medium.

Due to the significant selectivity for Cs+, ammonium molybdophosphate (AMP) possesses potential to uptake radiocesium from high-level liquid waste (HLLW), whereas its micro-crystalline structure and fine powder morphology limit its industrial application. Although the granulation method with alginate is prospective for the preparation of an AMP exchanger, the mechanical strength of obtained beads may be insufficient for application. In this context, we prepared silica-reinforced AMP-calcium alginate (ACS) beads and evaluated their performance for Cs+ removal from strong acidic solutions. It was found that the addition of silica in the fabrication significantly improved the mechanical strength of the beads in comparison to those without silica. Notably, the beads with an AMP/silica mass ratio of 1.0 exhibited an exceptional mechanical strength, surpassing that of ACS beads composed of other components. The batch experiment results indicated that the Cs+ adsorption follows a non-linear pseudo-second-order rate equation. The distribution coefficient of Cs+ was high even in extreme acidic conditions (∼1.6 × 102 mL/g in 8.0 mol/L HNO3 solution). The Cs+ adsorption can be well fitted with the Langmuir model, and the estimated maximum exchange capacity in 3.0 mol/L HNO3 could reach 23.9 mg/g. More importantly, ACS beads showed excellent selectivity toward Cs+ uptake over eight co-existing metal ions in simulated HLLW, with separation factor values all above 145. The column experiment exhibited that the beads can serve as the stationary phase in columns to effectively remove Cs+. The findings of this study are significant as they provide insights into the development of efficient materials for radiocesium removal from high-level liquid waste. The results demonstrate the potential of silica-reinforced ACS beads for Cs+ adsorption, with promising applications in industrial settings.

A fiber-optic spectroscopic setup for isomerization quantum yield determination.

A spectroscopic setup for isomerization quantum yield determination is reported. The setup combines fiber-coupled LEDs, a commercially calibrated thermopile detector for measurement of the photon flux, and a fiber-coupled UV-vis spectrometer. By solving the rate equations numerically, isomerization quantum yields can be obtained from the UV-vis absorption spectra. We show that our results for the prototypical photoswitch azobenzene are in excellent agreement with the literature. The analysis of the errors showed that the quantum yields determined using this method are in the same order of magnitude as when using actinometry, thus demonstrating the reliability of our setup.

Quantitative Kinetic Insights from Operando-UV/Vis Spectroscopy: An Application to NH3-SCR of NOx on Cu-CHA Catalysts.

We employ UV/Vis Diffuse Reflectance spectroscopy directly coupled with a packed bed flow reactor to extract quantitative kinetic information. We use as a show-case the CuII/CuI redox dynamics during the reduction half cycle of the NH3-Selective Catalytic Reduction (SCR) on Cu-CHA catalysts. Our measurements enable quantification of the fraction of oxidized Cu, reconstructed by Multivariate Curve Resolution (MCR) together with monitoring of the gas-phase evolution during the reaction. These data both on the dynamics of the gas-phase and of the active site oxidation state have been used to assess the reduction half cycle rate equation and estimate the rate constant. Our results in terms of reaction orders and kinetic constant are in line with previous findings in the literature. Overall, our results demonstrate that the combined analysis of the UV spectra and of the gas-phase dynamics provides converging and unparalleled kinetic insight: this approach effectively resolves ambiguities concerning RHC kinetics and mechanism. More in general, this work provides evidence that operando spectroscopy can be used to extract quantitative kinetic information on catalytic cycles.

Quantitative Kinetic Insights from Operando‐UV/Vis Spectroscopy: An Application to NH3−SCR of NOx on Cu‐CHA Catalysts

AbstractWe employ UV/Vis Diffuse Reflectance spectroscopy directly coupled with a packed bed flow reactor to extract quantitative kinetic information. We use as a show‐case the CuII/CuI redox dynamics during the reduction half cycle of the NH3‐Selective Catalytic Reduction (SCR) on Cu‐CHA catalysts. Our measurements enable quantification of the fraction of oxidized Cu, reconstructed by Multivariate Curve Resolution (MCR) together with monitoring of the gas‐phase evolution during the reaction. These data both on the dynamics of the gas‐phase and of the active site oxidation state have been used to assess the reduction half cycle rate equation and estimate the rate constant. Our results in terms of reaction orders and kinetic constant are in line with previous findings in the literature. Overall, our results demonstrate that the combined analysis of the UV spectra and of the gas‐phase dynamics provides converging and unparalleled kinetic insight: this approach effectively resolves ambiguities concerning RHC kinetics and mechanism. More in general, this work provides evidence that operando spectroscopy can be used to extract quantitative kinetic information on catalytic cycles.

How hot are weakly-bound cluster ions in a blackbody field? Insights from master equation modeling

Measuring accurate energetics in mass spectrometry thermochemical and calorimetry experiments depends on detailed knowledge of the energetics of the ion populations. For example, in cases where blackbody infrared radiative dissociation (BIRD) kinetics are not in the rapid energy exchange (REX) limit, threshold dissociation energies obtained directly from experiment will be too low. When ions are not in the REX limit, the ion internal energy distributions can be modeled using a master equation (ME). The ME allows evaluation of ion internal energies over time with a set of rate equations that describe the transfer of energy from one energy state to another. Here, ME modeling that accounts for the radiative absorption and emission, and dissociation rate constants is performed to determine the energetics of two model systems, M2+(H2O)n with n = 24, 55, 96, 178 and H+(AlaGly)n with n = 4, 8, 16, 32, activated by a blackbody field at temperatures between 120 and 200 K. The hydrated cluster and oligopeptide sizes are chosen such that respective ions have comparable number of internal degrees-of-freedom. The effects of blackbody temperature and inherent properties, such as frequencies and infrared (IR) intensities, molecule size, and dissociation parameters (threshold dissociation energy, E0, and high-pressure pre-exponential factor, A∞) on the resulting ion effective temperatures, steady-state energy distributions, and BIRD kinetics are explored. ME results show that at low blackbody temperatures (<∼140 K), the steady-state internal energy distributions of the ion populations resemble those of Boltzmann distributions at the blackbody temperature. At higher blackbody temperatures (>∼140 K), rapid dissociation causes the steady-state internal energy distributions to equilibrate to lower energies where absorption and emission are competitive with dissociation. This results in ion effective temperatures that deviate from and are “colder” than the blackbody temperatures. The temperature where this transition occurs depends on the competition among absorption, emission, and dissociation, and is controlled by the dissociation parameters, vibrational frequencies, and IR intensities, as illustrated for M2+(H2O)n and H+(AlaGly)n. This work shows that, under certain conditions, the ion effective temperatures can deviate significantly from those of the blackbody field temperatures. ME modeling can be used to determine the energy content of ion complexes in mass spectrometry experiments to improve the accuracy of thermochemical and calorimetry measurements of weakly-bound clusters and for more confident assignments of conformations and structures in action spectroscopy.