State Population Distributions Research Articles

Photodissociation dynamics of SO2 via the G̃1B1 state: The O(1D2) and O(1S0) product channels.

Produced by both nature and human activities, sulfur dioxide (SO2) is an important species in the earth's atmosphere. SO2 has also been found in the atmospheres of other planets and satellites in the solar system. The photoabsorption cross sections and photodissociation of SO2 have been studied for several decades. In this paper, we reported the experimental results for photodissociation dynamics of SO2 via the G̃1B1 state. By analyzing the images from the time-sliced velocity map ion imaging method, the vibrational state population distributions and anisotropy parameters were obtained for the O(1D2) + SO(X3Σ-, a1Δ, b1Σ+) and O(1S0) + SO(X3Σ-) channels, and the branching ratios for the channels O(1D2) + SO(X3Σ-), O(1D2) + SO(a1Δ), and O(1D2) + SO(b1Σ+) were determined to be ∼0.3, ∼0.6, and ∼0.1, respectively. The SO products were dominant in electronically and rovibrationally excited states, which may have yet unrecognized roles in the upper planetary atmosphere.

Abstract LB139: Disparities in oral precancerous lesion surveillance in the United States upper Midwest

Abstract Objective: To determine whether geographic representation and race of patients in a regional oral cancer surveillance program (University of Minnesota Cancer Active Surveillance Population (UMN CASP)) mirror characteristics in the corresponding National Cancer Institute (NCI) designated comprehensive cancer center catchment. Introduction: Oral cancer poses a significant public health concern that may be mitigated through lesion surveillance. Representation of patients for clinical trials throughout an NCI cancer center catchment area is a crucial goal to promote improved health outcomes. This study investigates the demographic landscape of patients with preneoplastic oral lesions seen at the CASP. Methods: Through the UMN Clinical and Translational Sciences Institute, we queried 30 International Classification of Disease (ICD) 9 and 10 codes corresponding to 120 unique mucosal oral precancerous lesion descriptors of CASP patients. Automated extraction of electronic medical record (EMR) data for 4,496 patients treated by the senior author between 2011 and 2023 identified 1,375 patients with preneoplastic lesions. The proportion of patients residing in three-digit zip code regions of Minnesota were compared to 2021 American Community Survey state population data. Additionally, race data were compared between CASP patients and the UMN Masonic Cancer Center (MCC) patient catchment data. Results: CASP patients were over-represented relative to state population distributions within the Minneapolis-St. Paul metropolitan area and surrounding suburbs (region 554 p<0.0001 and region 551 p<0.0001). Under-representation of CASP patients was observed in all western and southern border regions (regions 559 p<0.0001, 560 p<0.0001, 561 p<0.0001, 562 p=0.0037, 565 p<0.0001, and 567 p=0.0006) as well as portions of central (563 p<0.0001), northern (566 p=0.0015), and north-eastern (558 p<0.0001) Minnesota. Proportional representation was observed in several regions of central (553 and 564), eastern (550), and north-eastern (557 and 556) Minnesota. Comparisons of CASP race data revealed a higher proportion of black patients (CASP 8.59% [95% CI 7.17-10.27%] vs. MCC 7.16% [95% CI 7.14-7.17%]) and a lower proportion of Asian/Pacific Islander patients (CASP 3.74% [95% CI 2.82-4.94%] vs. MCC 5.32% [95% CI 5.30-5.34%]) relative to MCC catchment patients. White, American Indian/Alaskan Native, and mixed-race groups were proportionally represented in both data sets. Conclusions: These data show that system wide EMR searches can be implemented to identify patients in an NCI cancer center catchment area with precancerous or other at-risk conditions for cancer. Importantly, Native patients were proportionally represented in the screening program while several rural locations were under-represented. This information can instruct the expenditure of additional resources for under-represented groups and permit streamlined enrollment of patients for cancer prevention clinical trials. Citation Format: Alexander J. Dwyer, Lindsey Mortensen, Beverly R. Wuertz, Frank G. Ondrey. Disparities in oral precancerous lesion surveillance in the United States upper Midwest [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB139.

Quantifying noise effects in optical measures of excited state transport.

Time-resolved microscopy is a widely used approach for imaging and quantifying charge and energy transport in functional materials. While it is generally recognized that resolving small diffusion lengths is limited by measurement noise, the impacts of noise have not been systematically assessed or quantified. This article reports modeling efforts to elucidate the impact of noise on optical probes of transport. Excited state population distributions, modeled as Gaussians with additive white noise typical of experimental conditions, are subject to decay and diffusive evolution. Using a conventional composite least-squares fitting algorithm, the resulting diffusion constant estimates are compared with the model input parameter. The results show that heteroscedasticity (i.e., time-varying noise levels), insufficient spatial and/or temporal resolution, and small diffusion lengths relative to the magnitude of noise lead to a surprising degree of imprecision under moderate experimental parameters. Moreover, the compounding influence of low initial contrast and small diffusion length leads to systematic overestimation of diffusion coefficients. Each of these issues is quantitatively analyzed herein, and experimental approaches to mitigate them are proposed. General guidelines for experimentalists to rapidly assess measurement precision are provided, as is an open-source tool for customizable evaluation of noise effects on time-resolved microscopy transport measurements.

A Spectroscopic Thermometer: Individual Vibrational Band Spectroscopy with the Example of OH in the Atmosphere of WASP-33b

Individual vibrational band spectroscopy presents an opportunity to examine exoplanet atmospheres in detail, by distinguishing where the vibrational state populations of molecules differ from the current assumption of a Boltzmann distribution. Here, retrieving vibrational bands of OH in exoplanet atmospheres is explored using the hot Jupiter WASP-33b as an example. We simulate low-resolution spectroscopic data for observations with the JWST's NIRSpec instrument and use high-resolution observational data obtained from the Subaru InfraRed Doppler instrument (IRD). Vibrational band–specific OH cross-section sets are constructed and used in retrievals on the (simulated) low- and (real) high-resolution data. Low-resolution observations are simulated for two WASP-33b emission scenarios: under the assumption of local thermal equilibrium (LTE) and with a toy non-LTE model for vibrational excitation of selected bands. We show that mixing ratios for individual bands can be retrieved with sufficient precision to allow the vibrational population distributions of the forward models to be reconstructed. A fit for the Boltzmann distribution in the LTE case shows that the vibrational temperature is recoverable in this manner. For high-resolution, cross-correlation applications, we apply the individual vibrational band analysis to an IRD spectrum of WASP-33b, applying an “unpeeling” technique. Individual detection significances for the two strongest bands are shown to be in line with Boltzmann-distributed vibrational state populations, consistent with the effective temperature of the WASP-33b atmosphere reported previously. We show the viability of this approach for analyzing the individual vibrational state populations behind observed and simulated spectra, including reconstructing state population distributions.

Overview of Numerical Simulations for Calculating In-Plasma β-Decay Rates in the Framework of PANDORA Project

β-decay rates are essential inputs in stellar nucleosynthesis models to explain observed nuclear abundances. While current models continue to use terrestrial values, experiments in storage rings indicate strong divergence between decay rates of neutral and ionised atoms [1], necessitating renewed investigations into stellar decay rates. The PANDORA project aims at measuring lifetimes of specific radio-isotopes trapped in an ECR plasma (which mimics astrophysical environments to some extent) and compare them with theoretical predictions [2], consequently verifying the models and allowing decay rate estimation for any isotope in the stellar interior. We present here a simulation scheme to characterise the space-resolved charge state and level population distribution of buffer and radio-isotope ions in ECR ion sources in order to calculate in-plasma decay rates. The algorithm is based on a Particle-in-Cell Monte Carlo (PIC-MC) routine that simultaneously models charge transport with collision-radiative processes. Preliminary results from the simulation are also shown, along with important takeaways for code-optimisation.

Assessing Disparities in COVID-19 Testing Using National COVID Cohort Collaborative.

With NCATS National COVID Cohort Collaborative (N3C) dataset, we evaluated 14 billion medical records and identified more than 12 million patients tested for COVID-19 across the US. To assess potential disparities in COVID-19 testing, we chose ten US states and then compared each state's population distribution characteristics with distribution of corresponding characteristics from N3C. Minority racial groups were more prevalent in the N3C dataset as compared to census data. The proportion of Hispanics and Latinos in N3C was slightly lower than in the state census. Patients over 65 years old had higher representation in the N3C dataset and patients under 18 were underrepresented. Proportion of females in the N3C was higher compared with the state data. All ten states in N3C showed a higher representation of urban population versus rural population compared to census data.

Rotational and nuclear-spin level\xa0dependent photodissociation dynamics of H2S

The detailed features of molecular photochemistry are key to understanding chemical processes enabled by non-adiabatic transitions between potential energy surfaces. But even in a small molecule like hydrogen sulphide (H2S), the influence of non-adiabatic transitions is not yet well understood. Here we report high resolution translational spectroscopy measurements of the H and S(1D) photoproducts formed following excitation of H2S to selected quantum levels of a Rydberg state with 1B1 electronic symmetry at wavelengths λ ~ 139.1 nm, revealing rich photofragmentation dynamics. Analysis reveals formation of SH(X), SH(A), S(3P) and H2 co-fragments, and in the diatomic products, inverted internal state population distributions. These nuclear dynamics are rationalised in terms of vibronic and rotational dependent predissociations, with relative probabilities depending on the parent quantum level. The study suggests likely formation routes for the S atoms attributed to solar photolysis of H2S in the coma of comets like C/1995 O1 and C/2014 Q2.

Photodissociation Dynamics of H2O via the Ẽ' (1B2) Electronic State.

Photodissociation dynamics of H2O via the Ẽ'1B2 state were studied using the high-resolution H atom photofragment translational spectroscopy method, in combination with the tunable vacuum ultraviolet free electron laser (VUV FEL). The measured translational energy spectra allow us to determine the respective quantum state population distributions for the nascent OH(X2Π) and OH(A2Σ+) photofragments. Analyses of the quantum state population distributions show both the ground and electronically excited OH fragments to be formed with moderate vibrational excitation but with highly rotational excitation. Unlike the dissociation via the lower-lying electronic states, where OH(X) is the major fragment, the OH(A) products are predominant via the Ẽ' state. These products are mainly ascribed to a fast dissociation on the B̃1A1 state surface after nonadiabatic transitions from the initial excited Ẽ' state to the B̃ state. Meanwhile, another dissociation pathway from the Ẽ' state to the 1B2 3pb2 state, followed by coupling to the 1A2 3pb2 state, is also observed, which yields the OH(X) + H and O(3P) + 2H products.

Water Photolysis and Its Contributions to the Hydroxyl Dayglow Emissions in the Atmospheres of Earth and Mars.

Airglow is a well-known phenomenon in the Earth's upper atmosphere, which arises from the emissions of energetic atoms and molecules. The Meinel band emission from high vibrationally excited OH(X) radicals is one of the more important contributors to the airglow from the mesosphere/lower thermosphere. The H + O3 reaction has long been regarded as the dominant source of these OH(X, high v) radicals. Here we demonstrate that vacuum ultraviolet (VUV) photolysis of water vapor at λ ∼ 112.8 nm represents another source of exceptionally highly vibrationally excited OH(X) radicals, with a nascent vibrational state population distribution that maximizes at v = 9 and extends to at least the v = 15 level. Atmospheric chemistry modeling indicates that OH(X, high v) radicals from H2O photolysis might be detectable in the OH Meinel band dayglow in the upper atmosphere of Earth and should dominate the corresponding emission from the Martian atmosphere. VUV photolysis of H2O also produces electronically excited OH(A) radicals, and simultaneous detection of emissions from OH(X, high v) and OH(A) is shown to offer a route to identifying high-oxygen exoplanetary atmospheres.

Modeling of laser produced Zn plasma with detailed electron impact fine structure excitation cross-sections

An intricate collisional radiative (CR) model is developed including all the important processes for the laser induced zinc plasma. The electron impact excitation (EIE) and de-excitation of several fine structure levels of Zn play a dominant role in the laser induced plasma and their cross-sections are needed. In view of this, an extensive calculation is performed to obtain the EIE cross-sections of the large number of fine structure transitions of zinc atom. The cross-sections of Zn are calculated and presented for the excitations from its ground state 4s2 (J = 0) as well as from the 4s4p excited state to the various fine structure levels of different excited states using fully relativistic distorted wave (RDW) theory. In the calculation, relativistic multi-configuration bound target atomic wave functions are obtained through GRASP2K program using 4s2, 4s4p, 4s5s, 4s5p, 4s4d, 4s6s, 4s6p, 4s5d, 4s7s and 4s7p configuration state functions while the projectile incident and scattered electron distorted wave functions are obtained by solving the relativistic Dirac equations. Further, the calculated cross-sections are incorporated in the CR model for the plasma characterization as the various rate coefficients are linked through their corresponding cross-sections. The model gives the state population distribution of the fine structure energy levels of the neutral Zn atom considered in the model and from which the intensities of the line emissions are obtained. The calculated intensities from the CR model for the four emission lines (334.5, 468, 472, and 481 nm) are matched with the spectroscopic measurements (Smijesh et al 2013 J. Appl. Phys. 114 093301) and the plasma parameters viz electron density and electron temperature are evaluated. The plasma parameters are presented at different ambient pressures in the range of 0.05–10 Torr.

Exhaustive state-to-state cross sections for reactive molecular collisions from importance sampling simulation and a neural network representation.

High-temperature, reactive gas flow is inherently nonequilibrium in terms of energy and state population distributions. Modeling such conditions is challenging even for the smallest molecular systems due to the extremely large number of accessible states and transitions between them. Here, neural networks (NNs) trained on explicitly simulated data are constructed and shown to provide quantitatively realistic descriptions which can be used in mesoscale simulation approaches such as Direct Simulation Monte Carlo to model gas flow at the hypersonic regime. As an example, the state-to-state cross sections for N(4S) + NO(2Π) → O(3P) + N2(X1Σg +) are computed from quasiclassical trajectory (QCT) simulations. By training NNs on a sparsely sampled noisy set of state-to-state cross sections, it is demonstrated that independently generated reference data are predicted with high accuracy. State-specific and total reaction rates as a function of temperature from the NN are in quantitative agreement with explicit QCT simulations and confirm earlier simulations, and the final state distributions of the vibrational and rotational energies agree as well. Thus, NNs trained on physical reference data can provide a viable alternative to computationally demanding explicit evaluation of the microscopic information at run time. This will considerably advance the ability to realistically model nonequilibrium ensembles for network-based simulations.

The pure effect of social preferences on regional location choices: The evolving dynamics of convergence to a steady state population distribution

AbstractThis paper tracks the consequences of individuals’ desire to align their location with their social preferences. The social preference studied in the paper is distaste for relative deprivation, measured in a cardinal manner. Location is conceived as social space, with individuals choosing to relocate if, as a result, their relative deprivation will be reduced, holding their incomes constant. Conditions are provided under which the associated dynamics reaches a spatial steady state, the number of periods it takes to reach a steady state is specified, and light is shed on the robustness of the steady state outcome. By way of simulation it is shown that for large populations, a steady state of the relocation dynamics is almost always reached, typically in one period, and that cycles are more likely to occur when the populations’ income distributions are more equal.

The Pure Effect of Social Preferences on Regional Location Choices: The Evolving Dynamics of Convergence to a Steady State Population Distribution

This paper tracks the consequences of individuals' desire to align their location with their social preferences. The social preference studied in the paper is distaste for relative deprivation, measured in a cardinal manner. Location is conceived as social space, with individuals choosing to relocate if, as a result, their relative deprivation will be reduced, holding their incomes constant. Conditions are provided under which the associated dynamics reaches a spatial steady state, the number of periods it takes to reach a steady state is specified, and light is shed on the robustness of the steady state outcome. By way of simulation it is shown that for large populations, a steady state of the relocation dynamics is almost always reached, typically in one period, and that cycles are more likely to occur when the populations' income distributions are more equal.

The Pure Effect of Social Preferences on Regional Location Choices: The Evolving Dynamics of Convergence to a Steady State Population Distribution

This paper tracks the consequences of individuals’ desire to align their location with their social preferences. The social preference studied in the paper is distaste for relative deprivation, measured in a cardinal manner. Location is conceived as social space, with individuals choosing to relocate if, as a result, their relative deprivation will be reduced, holding their incomes constant. Conditions are provided under which the associated dynamics reaches a spatial steady state, the number of periods it takes to reach a steady state is specified, and light is shed on the robustness of the steady state outcome. By way of simulation it is shown that for large populations, a steady state of the relocation dynamics is almost always reached, typically in one period, and that cycles are more likely to occur when the populations’ income distributions are more equal.

Normal-state properties of a resonantly interacting p -wave Fermi gas

Motivated by recent experimental progress, we make an investigation of p- and d-wave resonant Bose gas. An explantation of the Nozieres and Schmitt-Rink (NSR) scheme in terms of two-channel model is provided. Different from the s-wave case, high partial wave interaction supports a quasi-bound state in the weak coupling regime. Within the NSR approximation, we study the equation of state, critical temperature and particle population distributions. We clarify the effect of the quasi-bound state on the phase diagram and the dimer production. A multi-critical point where normal phase, atomic superfluid phase and molecular superfluid phase meet is predicted within the phase diagram. We also show the occurrence of a resonant conversion between solitary atoms and dimers when temperature kBT approximates the quasi-bound energy.

Measuring Aspects of Mobility, Polarization and Convergence in the Absence of Cardinality: Indices Based Upon Transitional Typology

Social Mobility, Equality of Opportunity, Polarization, Convergence and Segmentation can each be construed as describing a particular transitional process between departure and arrival state population distributions. Frequently indices of their extent are based upon variables that have cardinal measure, however often the terms apply to groupings that are ordinal or categorical, devoid of meaningful cardinal distance, relating to transitions between non-comparable states (as with generational transitions from parental socio-economic class to a child’s educational or health status). In such contexts measurement must rely upon the anatomy of the transition process without dependence on cardinal measure. Accordingly, here indices and tests, applicable in both cardinal and ordinal environments, based upon the structure of an underlying transition process are proposed and implemented. The tools have diverse application, in illustration 3 examples from Canadian Generational relationships, the world size distribution of Gross National Product per capita and Chinese Social to Educational Class Structures are employed revealing many interesting features of transitional behaviors.

Optical field induced rotation of polarization in rubidium atoms with the additional magnetic field

We present the magnetic and optical field induced rotation of polarization in 87Rb and 85Rb atoms at geophysical magnetic fields. The line shape varies considerably in the presence of a magnetic field of the order of a few mG. Multiple Zeeman sublevel EIT systems involving rubidium atoms are investigated. Theoretical formalism of optical field induced polarization rotation in the presence of a magnetic field is discussed by considering all the Zeeman sublevels. It is noted that the ground state population distribution also plays a major role.

Manipulating excited state hyperfine level populations in an atomic laser through electronic spin polarization: controlling upper laser level degeneracy and small Signal Gain.

Anisotropic coherent radiation has been generated from an isotropic medium, in the absence of an external magnetic field, by the spin polarization of an atomic excited state. Lasing on specific hyperfine lines of the 6p2P32→6s2S12 (D2) transition of Cs at 852.1 nm has been realized by photoexciting Cs-rare gas thermal collision pairs with a circularly-polarized (σ+) optical field. Subsequent dissociation of the transient Cs-rare gas B2Σ12+ diatomic molecule selectively populates the F = 4, 5 hyperfine levels of the Cs 6p2P32 state. Not only does electronic spin polarization of the upper laser level yield circularly-polarized coherent emission, but the effective degeneracy (g2) of the 6p2P32 state is altered by the non-statistical hyperfine state population distribution, thereby permitting control of the laser small signal gain with an elliptically-polarized pump optical field. The D2 laser efficiency and output power correlate directly with the molecular orbital structure of the Cs-rare gas B2Σ+ state in the region of internuclear separation at which the diatomic complex is born.

Activated Dissociation of HCl on Au(111).

We report zero-coverage reaction probabilities (S0) for HCl dissociative adsorption on Au(111) obtained by the seeded molecular beam hot-nozzle method. For measurements at normal incidence with mean translational energies ranging from 0.94 to 2.56 eV (nozzle temperatures 296 to 1060 K), S0 increased from 6 × 10(-6) to 2 × 10(-2). S0also increased with increasing nozzle temperature for fixed incidence energy associated with the motion normal to the surface. Accounting for the influence of the vibrational state population and translational energy distributions in the incident beam, we are able to compare the experimental results to recent theoretical predictions. These calculations, performed employing 6-D quantum dynamics on an electronically adiabatic potential energy surface obtained using density functional theory at the level of the generalized gradient approximation and the static surface approximation, severely overestimate the reaction probabilities when compared with our experimental results. We discuss some possible reasons for this large disagreement.

A 1 + 1' resonance-enhanced multiphoton ionization scheme for rotationally state-selective detection of formaldehyde via the à (1)A2 ← X[combining tilde] (1)A1 transition.

The formaldehyde molecule is an important model system for understanding dynamical processes in small polyatomic molecules. However, prior to this work, there have been no reports of a resonance-enhanced multiphoton ionization (REMPI) detection scheme for formaldehyde suitable for rovibrationally state-selective detection in molecular beam scattering experiments. Previously reported tunable REMPI schemes are either non-rotationally resolved, involve multiple resonant steps, or involve many-photon ionization steps. In the current work, we present a new 1 + 1' REMPI scheme for formaldehyde. The first photon is tunable and provides rotational resolution via the vibronically allowed à (1)A2 ← X[combining tilde] (1)A1 transition. Molecules are then directly ionized from the à state by one photon of 157 nm. The results indicate that the ionization cross section from the 4(1) vibrational level of the à state is independent of the rotational level used as intermediate, to within experimental uncertainty. The 1 + 1' REMPI intensities are therefore directly proportional to the à ← X[combining tilde] absorption intensities and can be used for quantitative measurement of X[combining tilde]-state population distributions.