NewSenior AI/ML Engineer JobotSenior AI/ML EngineerMcLean, VARemote$140,000–$180,000 / yearInformation collected and processed as part of your Jobot candidate profile, and any job applications, resumes, or other information you choose to submit is subject to Jobot's Privacy Policy, as well as the Jobot California Worker Privacy Notice and Jobot Notice Regarding Automated Employment Decision Tools which are available at jobot.com/legal. You’ll design and build our machine learning infrastructure - starting with vector search and retrieval-augmented generation and expanding into fine-tuned LLMs with human feedback loops.
Computer Vision Engineer JobotComputer Vision EngineerHerndon, VA$125,000–$160,000 / yearInformation collected and processed as part of your Jobot candidate profile, and any job applications, resumes, or other information you choose to submit is subject to Jobot's Privacy Policy, as well as the Jobot California Worker Privacy Notice and Jobot Notice Regarding Automated Employment Decision Tools which are available at jobot.com/legal. This is a permanent position in the autonomous systems industry where you will be instrumental in developing, implementing, and optimizing cutting-edge computer vision systems.
NewSr Energy Engineer - DC JobotSr Energy Engineer - DCWashington, DC$90,000–$155,000 / yearProject Managers work independently on complex projects, network to expand the market outreach for Existing Building Decarbonization projects, and collaborate closely with clients, contractors, and internal teams. – Lead energy modeling and building performance simulations and perform life-cycle cost analyses to evaluate the ROI and overall economic feasibility of various decarbonization strategies, including high-efficiency HVAC systems and the integration of geothermal and other renewable energy sources.
Electrical Engineer II (VA) GCR Professional ServicesElectrical Engineer II (VA)Chantilly, Virginia$40–$50 / hourContractorProject Management: Plan and manage electrical engineering projects, including creating project timelines, allocating resources, and coordinating with cross-functional teams. Collaboration: Collaborate with other engineers, technicians, and professionals to integrate electrical systems into larger projects or products.
NewSenior Applications Engineer CredenceSenior Applications EngineerTysons, VATo succeed in this role, you should combine deep hands-on engineering expertise with modern front-end skills, the ability to guide development teams, improve existing systems, and enforce disciplined configuration management practices in support of DAAS AI/ML modernization efforts. You will manage software development and support efforts using formal specifications, data flow diagrams, and other accepted design techniques and Computer-Aided Software Engineering (CASE) tools, while providing reliable cost and schedule estimates to program leadership.
Quantum Engineer SME DCS CorporationQuantum Engineer SMESpringfield, VAPerform trade studies and conduct analyses to evaluate proposed quantum machine learning approaches, review technical reports, assess product-quality impacts, and characterize performance using quantum simulation or related technologies to support verification and quality assurance. The DCS Air and Space Technology Sector are seeking a qualified candidate to apply subject matter expertise in the areas of quantum engineering, analysis, and system design of complex programming projects supporting National Agencies.
Systems Engineer III BASE ONESystems Engineer IIIArlington, VA$130,000–$175,000 / yearContractorConducting capability-based research into commercial and non-commercial technology solutions that address customer identified technology needs. Evaluations may include hands-on capability testing of trial licenses and open-source capabilities.
NewSenior Cybersecurity Engineer DCS CorporationSenior Cybersecurity EngineerDahlgren, VAThe Senior Cybersecurity Engineer leverages in-depth understanding and experience in cybersecurity requirements development, cyber threat analysis, cyber engineering, cyber systems architecture development and cybersecurity policy development experience. to facilitate security engineering tasks in support of the customer’s system security objectives. Requires a minimum of 5 years program specific security engineering experience working with Navy afloat/tactical combat systems or 13 years of general security engineering experience.
NewAudio AI Engineer Dev Technology GroupAudio AI EngineerWashington, DC$80,000–$160,000 / yearAs a Washington Post Top Workplace award winner for the past THIRTEEN years in a row, the Top Workplaces USA for the past five years, and a recipient of the Companies As Responsive Employers (CARE) Award for the past six years, Dev Technology employees enjoy: Generous and flexible time-off policy. Documentation & communication: Produce clear model cards, dataset documentation, and evaluation write-ups that let technical and non-technical stakeholders understand what the model does, how it compares to alternatives, and what its risks and limitations are.
NewEngineer; Cloud Systems or Architect, Cloud Systems GCP (Google Cloud Professional) (SME) PlanIT GroupEngineer; Cloud Systems or Architect, Cloud Systems GCP (Google Cloud Professional) (SME)Reston, VAClient CIO Architecture, Strategy & Innovation (CASI) is responsible to assist Vice President of Information Technology (IT) design, develop, maintain, support, and translate corporate business vision and strategy along with stakeholder input into objectives for building, enhancing, or replacing business and IT systems capabilities, together with an implementation of a comprehensive IT roadmap, all-the-while maintaining resilience to change as a key architectural and strategy objective for the enterprise. • Tasks – might include (neither exhaustive nor restrictive): o Advises and assists IT functional groups to define and implement solutions aligned with a Cloud based Microservices / Service Oriented Architecture (SOA) for infrastructure or business applications.
NewSenior Software Engineer JobotSenior Software EngineerWest McLean, VA$140,000–$215,000 / yearWith first hand knowledge of problems that arise deploying software with millions of concurrent users worldwide, this paradigm changing tool will enable engineers to quickly, efficiently, and reliably develop and deploy large scale distributed systems autonomously. Information collected and processed as part of your Jobot candidate profile, and any job applications, resumes, or other information you choose to submit is subject to Jobot's Privacy Policy, as well as the Jobot California Worker Privacy Notice and Jobot Notice Regarding Automated Employment Decision Tools which are available at jobot.com/legal.
NewIoT Engineer System OneIoT EngineerMerrifield, VARemote$80 / hourPartner with sensor specialists to manage new sensor data streaming to the IoT platform, and with data scientists and machine learning engineers to take on analytic results and develop it to an application with a user interface, integrate with any pre-existing systems, demonstrate successful use cases and wins, etc. Work with Industry solution providers, equipment manufacturers, and the Enterprise Resource Planning vendor to design and implement the required system integration points and data flow to achieve best-in-class lights-out operations.
Computational Protein Engineer Gables Search GroupComputational Protein EngineerRockville, MD$125,000–$165,000We are recruiting for a research-driven biotechnology organization seeking a Computational Protein Engineer to lead hands-on antibody and protein engineering programs in Rockville, Maryland. This position combines wet-lab experimentation with computational design tools to accelerate discovery, guide design decisions, and improve experimental outcomes.
NewLead Specialist, Federal Data Engineer KPMGLead Specialist, Federal Data EngineerWashington, DCIf you're looking for a firm with a strong team connection where you can be your whole self, have an impact, advance your skills, deepen your experiences, and have the flexibility and access to constantly find new areas of inspiration and expand your capabilities, then consider a career in Advisory. These include the duties and responsibilities listed above, as well as the abilities to adhere to company policies, exercise sound judgment, effectively manage stress and work safely and respectfully with others, exhibit trustworthiness, and safeguard business operations and company reputation.
Senior MLOps Engineer JobotSenior MLOps EngineerSterling, VA$150,000–$175,000 / yearInformation collected and processed as part of your Jobot candidate profile, and any job applications, resumes, or other information you choose to submit is subject to Jobot's Privacy Policy, as well as the Jobot California Worker Privacy Notice and Jobot Notice Regarding Automated Employment Decision Tools which are available at jobot.com/legal. Operate the AI infrastructure layer: self-hosted observability and evaluation tooling (Langfuse), product telemetry, model gateway and per-workload routing, and compliant GovCloud inference paths.
M365 Engineer LeidosM365 EngineerBethesda, MD$107,900–$195,050Engineer, administer, and provide lifecycle support for Microsoft 365 (government community cloud (GCC) services including but not limited to: Entra ID (Azure AD), Exchange Online, Intune, Teams, Power Platform, Purview. Leidos Dig Mod Health IT division is seeking a skilled and collaborative M365 Engineer to support the HHS enterprise by managing all aspects of Microsoft 365 Government Community Cloud (GCC) Software as a Service (SAAS) offering.
Systems Engineer LeidosSystems EngineerRockville, MD$87,100–$157,450If you received an email purporting to be from Leidos that asks for payment-related information or any other personal information (e.g., about you or your previous employer), and you are concerned about its legitimacy, please make us aware immediately by emailing us at LeidosCareersFraud@leidos.com. April 28, 2026For U.S. Positions: While subject to change based on business needs, Leidos reasonably anticipates that this job requisition will remain open for at least 3 days with an anticipated close date of no earlier than 3 days after the original posting date as listed above.
Business Process Re-engineering Specialist CredenceBusiness Process Re-engineering SpecialistMcLean, VAYou will provide facilitation, training, methodology development and evaluation, business process reengineering across all phases, identify best practices, support change management initiatives, apply business management techniques, contribute to organizational development efforts, perform activity and data modeling, and support information systems development methods and practices. Computer Science, Engineering, or Information Systems/Technology) and a specific logistics function (e.g., finance, supply, contract administration, transportation and operations research) and first-hand knowledge of the following: DoD/Component policies.
IEEE/Wi-Fi Standards Senior Research Engineer OfinnoIEEE/Wi-Fi Standards Senior Research EngineerReston, VAFull timeExperience developing physical/MAC layer protocols/procedures – channel access mechanism (e.g., LBT/FBE), OFDM/OFDMA, MIMO, dual-band operation, channel access mechanisms for mmWave frequencies, multi-beam operation, positioning, power saving techniques. This position focuses on researching and optimizing Wi-Fi transmission and reception mechanisms, as well as developing novel algorithms based on IEEE 802.11, Wi-Fi alliance (WFA), and 802.15 protocols.
NewSenior Research Engineer, Video Compression OfinnoSenior Research Engineer, Video CompressionReston, VAThis role is hands-on and implementation-heavy, working closely with internal teammates and external partners to deliver reproducible results and measurable impact. Hands-on experience in one or more video coding tool areas, including intra prediction, inter prediction, transform/quantization, in-loop filtering, and high-level syntax.
NewPrincipal Research Engineer, 3D Gaussian Splat Coding OfinnoPrincipal Research Engineer, 3D Gaussian Splat CodingReston, VAKey Responsibilities: As a Principal Research Engineer in 3D Gaussian Splatting, you will: Define and drive high-impact 3DGS coding directions, setting technical priorities across multiple workstreams and aligning execution across the team. Lead end-to-end design and evaluation of coding approaches for 3DGS representations (e.g., representation design, parameterization, quantization, entropy/context modeling, progressive transmission, complexity reduction), including tool interactions and system-level tradeoffs.
NewSenior Staff Research Engineer, 3D Gaussian Splat Coding OfinnoSenior Staff Research Engineer, 3D Gaussian Splat CodingReston, VACollaborate cross-team to remove blockers, integrate tool interactions, and improve shared infrastructure (pipelines, scripts, datasets, configurations, regression tests). Design and evaluate novel coding tools for 3DGS representations (e.g., geometry/attribute representation, parameter quantization, entropy modeling, structure/cluster coding, streaming and progressive refinement).
Principal Research Engineer, Video Compression OfinnoPrincipal Research Engineer, Video CompressionReston, VALead and coordinate technical initiatives across the team to remove blockers, manage tool interactions, and strengthen shared infrastructure (e.g., testing pipelines, scripts, datasets, and configurations). Preferred: Hands-on experience in multiple video coding tool areas, including intra prediction, inter prediction, transform/quantization, in-loop filtering, and high-level syntax.
6G Standards Research Engineer Ofinno6G Standards Research EngineerReston, VAFull timeStrong interpersonal skills, including active listening, fostering mutual respect, and building positive relationships with colleagues and stakeholders. You will be a part of innovative research projects, foster cross-disciplinary collaboration, and help position Ofinno as a trailblazer in the future of telecommunications.
6G System Architecture Research Engineer Ofinno6G System Architecture Research EngineerReston, VAFull timeStrong interpersonal skills, including active listening, fostering mutual respect, and building positive relationships with colleagues and stakeholders. You will be a part of innovative research projects, foster cross-disciplinary collaboration, and help position Ofinno as a trailblazer in the future of telecommunications.
NewSenior Staff Research Engineer, Neural Network Video Coding OfinnoSenior Staff Research Engineer, Neural Network Video CodingReston, VAHands-on experience in one or more video coding tool areas, including neural in-loop filtering, neural prediction, learned transforms, or end-to-end neural video compression. Collaborate cross-team to remove blockers, integrate tool interactions, and improve shared infrastructure (e.g., testing pipelines, scripts, datasets, and configurations).
PLATS - Sensor Platforms - Research Engineer Select Search AssociatesPLATS - Sensor Platforms - Research EngineerBethesda, MarylandServe as a liaison between performers, Test & Evaluation contributors, government and transition partners; Provide support for program related requirements for systems integration, design, development, modeling and simulation, data analytics and architecture design; Stay current on advances in technologies relevant to the research programs and perform technical studies as requested on topics of interest to the program managers. Required: Bachelors' degree in electrical engineering, mechanical engineering, aerospace engineering, computer engineering, applied physics, systems engineering, or a related technical field, with six plus (6+) years of work experience in one of these fields, or Masters' degree with two plus (2+) years of work experience.
Radar Research Engineer KBR IncRadar Research EngineerChantilly, VAProvide demonstrated skill in conceiving, planning and conducting research and analysis in difficult technological problem areas of considerable scope and complexity requiring unconventional or novel approaches and sophisticated research techniques. Candidates will have demonstrated an ability to make decisions independently on research and development (R&D) engineering problems and methods, in resolving important questions, and planning and coordinating work.
NewApplied Research Engineer U.S. Department of CommerceApplied Research EngineerWashington, DC$85,447–$133,142 / yearRelated curriculum -- Successful completion of a curriculum leading to a bachelor\''s degree in an appropriate scientific field, e.g., engineering technology, physics, chemistry, architecture, computer science, mathematics, hydrology, or geology, may be accepted in lieu of a bachelor\''s degree in engineering, provided the applicant has had at least 1 year of professional engineering experience acquired under professional engineering supervision and guidance. Specified academic courses -- Successful completion of at least 60 semester hours of courses in the physical, mathematical, and engineering sciences and that included the courses specified in the basic requirements under paragraph A. The courses must be fully acceptable toward meeting the requirements of an engineering program as described in paragraph A. \t.
Senior Vulnerability Research Engineer Parsons CorpSenior Vulnerability Research EngineerVA$148,300–$266,900 / yearWe promote a culture of excellence and close-knit teams that take pride in delivering, protecting, and sustaining our nation''s most critical assets, from Earth to cyberspace. Required Qualifications: Bachelor's degree in related technical field and 10+ years of professional related experience; Master's degree in related field will be considered in lieu of 4 years on experience.
Vulnerability Research Engineer Parsons CorpVulnerability Research EngineerVA$103,500–$181,100 / yearWe promote a culture of excellence and close-knit teams that take pride in delivering, protecting, and sustaining our nation''s most critical assets, from Earth to cyberspace. Our intelligent employees drive the state of the art as they provide services and solutions in the areas of defense, security, intelligence, infrastructure, and environmental.
Research Engineer Galois, Inc.Research EngineerArlington, VAWith clients including NASA, DARPA, AWS, and the DoW, we leverage our cutting-edge research to deliver high assurance solutions and tools that enhance security, reliability, and operational efficiency across sectors including aerospace & defense, healthcare, semiconductors, and fintech. Who We Are: From building digital engineering tools that make space exploration safer to verifying cryptographic libraries that protect some of the world’s most valuable data, Galois develops technology to guarantee the trustworthiness of systems where failure is unacceptable.
Frontier AI Research Engineer, Lead Booz Allen HamiltonFrontier AI Research Engineer, LeadMcLean, Virginia$128,700–$292,000 / yearOnsite : If this position is listed as onsite, work will primarily be performed at a Booz Allen office or customer facility, where employees will collaborate directly with colleagues and customers as required by the role. The Lead Engineer translates frontier concepts into working systems, ensures technical excellence across prototypes, and serves as the lab’s senior-most hands-on engineering authority.
Sr Research Engineer VeriSign IncSr Research EngineerReston, VA$164,300–$222,300 / yearThe Sr Engineer - Research Engineering plays a lead technical role in identifying and developing novel and operationally relevant research concepts related to Internet infrastructure applications and protocols. Represents Verisign in related external forums to build our reputation as an industry thought leader; publicizes research results in appropriate internal and external forums.
Research Engineer VeriSign IncResearch EngineerReston, VA$108,900–$147,300 / yearThe Engineer III - Research Software Engineer plays a role in identifying and developing novel and operationally relevant research concepts related to Internet infrastructure applications and protocols. Represents Verisign in related external forums to build our reputation as an industry thought leader; publicizes research results in appropriate internal and external forums.
Software Research Engineer RF Machine Learning (RFML) Peraton IncSoftware Research Engineer RF Machine Learning (RFML)College Park, MD$104,000–$166,000 / yearExperience supporting engineering best practices and research-to-prototype workflows: Linux, Git-based development, CI/CD (e.g., Jenkins), Agile development practices, containerization (Docker), reproducible experimentation. Experience designing or implementing database/repository interfaces, including performance-oriented querying (SQL and/or NoSQL), schema design, and data pipeline awareness.
Vulnerability Research Engineer Integration Innovation, Inc.Vulnerability Research EngineerWashington, D.C.$115,000–$181,000 / yearFull timeAbout i3: i3 is a technically diverse, 100% team member owned business, headquartered in Huntsville, Alabama specializing in missile and aviation systems engineering and logistic services, electronic warfare and electromagnetic effects analysis, UAS system integration and flight operations, full lifecycle C5ISR engineering services, cybersecurity and IT/IA innovative solutions and virtual training, simulation & serious game development and implementation. We have established a broad offering of products and capabilities collectively providing decades of experience supporting the full complement of DoD military services, Missile Defense Agency, National Aeronautics and Space Administration, and a variety of other Government organizations and private industry customers.
SETA/Research Engineer ATR, LLCSETA/Research EngineerBethesda, MarylandFull timeSETA/Research EngineerLocation: Bethesda, MDEligibility: Candidate must possess an active TS/SCI w/ CI Polygraph clearanceJob Description: We are seeking a Scientific, Engineering, and Technical Assistance (SETA) Support Specialist to join our team in support of a government research organization dedicated to investing in high-risk, high-payoff research programs to tackle some of the most difficult challenges of national security. Two (2) years of experience or equivalent education using test and measurement equipment relevant to advanced sensing technologies, such as spectrum analyzers, oscilloscopes, RF test platforms, wireless communications testbeds, biometric sensor test systems, or commercial off‑the‑shelf sensing devices.
Senior Research Engineer, Threat Intelligence SecurityScorecard IncSenior Research Engineer, Threat IntelligenceWashington, DCFounded in 2013 by security and risk experts Dr. Alex Yampolskiy and Sam Kassoumeh and funded by world-class investors, SecurityScorecard's patented rating technology is used by over 25,000 organizations for self-monitoring, third-party risk management, board reporting, and cyber insurance underwriting; making all organizations more resilient by allowing them to easily find and fix cybersecurity risks across their digital footprint. The work that matters most here is often the unglamorous part: retrieval grounded in the team''s own corpus so outputs cite sources rather than model priors, schema-constrained output so a generated indicator is a valid one, and eval harnesses that catch regressions before analysts do.
NewConcrete Research Engineer Genex SystemsConcrete Research EngineerMcLean, VA$80,000–$124,000 / yearIts work spans full-scale testing of bridges and bridge components, field evaluation of in-service structures, and forensic investigation of structural failures for state Departments of Transportation, FHWA divisions, and the National Transportation Safety Board (NTSB) — determining root causes of bridge failures and developing practices to prevent them from happening again. Genex Systems is hiring a Concrete Research Engineer to plan and conduct structural research projects for the Federal Highway Administration (FHWA) in the Structures Laboratory at the Turner-Fairbank Highway Research Center (TFHRC), the nation's premier highway research facility.
NewHydraulics Research Engineer Genex SystemsHydraulics Research EngineerMcLean, VA$80,000–$124,000 / yearGenex Systems has an immediate opening for a Hydraulics Research Engineer to support the Federal Highway Administration (FHWA) at the J. Sterling Jones Hydraulics Research Laboratory, part of the Turner-Fairbank Highway Research Center (TFHRC), the nation's premier highway research facility. You'll work hands-on with the lab's Multifunctional Flume System (MFS), testing scour around piers, abutments, and other bridge components, using advanced instrumentation including laser scanners, Acoustic Doppler Velocimeters (ADVs), Ultrasonic Doppler Velocimetry (UDVs), and Particle Image Velocimetry (PIV).
Software Research Engineer - RF Machine Learning (RFML) PeratonSoftware Research Engineer - RF Machine Learning (RFML)College Park, Maryland$104,000–$166,000 / yearFull timeExperience designing or implementing database/repository interfaces, including performance-oriented querying (SQL and/or NoSQL), schema design, and data pipeline awareness. Experience supporting engineering best practices and research-to-prototype workflows: Linux, Git-based development, CI/CD (e.g., Jenkins), Agile development practices, containerization (Docker), reproducible experimentation.
Senior Advanced AI Research Engineer Accenture PlcSenior Advanced AI Research EngineerArlington, VAThe Work: Applied Research & Innovation: Investigate active innovation frontiers in agentic AI systems - for example, agent memory and knowledge persistence architectures, model selection and inference routing strategies, autonomy and goal-anchoring control planes, and long-horizon task reliability. Translational Engineering: Translate research findings into production-grade implementations: engineered Python services, Node.js/TypeScript SDK modules, or platform-integrated components that other engineers and agent workloads depend on.
NewVulnerability Research Engineer Quadrant IncVulnerability Research EngineerWashington, DCUse static and dynamic analysis (disassembly, debugging, tracing, emulation) to map control flow, data structures, protocols, and algorithms. Collaborate with multi-disciplinary engineers (EW, RF/DSP, embedded, test) to translate reverse-engineering results into actionable engineering decisions.
Senior Data Scientist / AI Machine Learning Research Engineer CACISenior Data Scientist / AI Machine Learning Research EngineerSterling, Virginia$113,200–$237,800 / yearJob Title: Senior Data Scientist / AI Machine Learning Research EngineerJob Category: ScienceTime Type: Full timeMinimum Clearance Required to Start: TS/SCIEmployee Type: RegularPercentage of Travel Required: Up to 10%Type of Travel: Continental US* * * The Opportunity: CACI has an exciting new opportunity for a Senior AI and Machine Learning Research Engineer. Pay Range : There are a host of factors that can influence final salary including, but not limited to, geographic location, Federal Government contract labor categories and contract wage rates, relevant prior work experience, specific skills and competencies, education, and certifications.
Software Research Engineer Peraton IncSoftware Research EngineerSilver Spring, MD$135,000–$216,000 / yearResponsible for designing, testing, coding, and developing solutions to meet customer needs; ensuring software continues to function normally through software maintenance, upgrade, and testing; documenting the application, service, and environment as a reference for future operations and maintenance, including version and platform upgrades. Peraton Labs'' cybersecurity research protects mission-critical systems and national cyber infrastructure through a broad range of initiatives in computer network defense, secure-by-design techniques and cyber operations and experimentation platforms.
Windows Kernel & Vulnerability Research Engineer The Josef GroupWindows Kernel & Vulnerability Research EngineerChantilly, VirginiaConduct in-depth research into Windows internals , including system architecture, memory management, drivers, processes, and kernel-mode operations. Strong understanding of Windows operating system internals , including kernel architecture, drivers, APIs, memory layout, and subsystem behavior.
Software Research Engineer PeratonSoftware Research EngineerSilver Spring, Maryland$135,000–$216,000 / yearFull timeResponsible for designing, testing, coding, and developing solutions to meet customer needs; ensuring software continues to function normally through software maintenance, upgrade, and testing; documenting the application, service, and environment as a reference for future operations and maintenance, including version and platform upgrades. Peraton Labs' cybersecurity research protects mission-critical systems and national cyber infrastructure through a broad range of initiatives in computer network defense, secure-by-design techniques and cyber operations and experimentation platforms.
Senior Data Scientist / AI Machine Learning Research Engineer CACI International IncSenior Data Scientist / AI Machine Learning Research EngineerSterling, VA$82,100–$172,400 / yearPay Range: There are a host of factors that can influence final salary including, but not limited to, geographic location, Federal Government contract labor categories and contract wage rates, relevant prior work experience, specific skills and competencies, education, and certifications. Proficiency in designing and building data pipelines, including experience with ETL processes, data warehousing solutions, and optimizing workflows for large-scale data processing.
Senior Research Engineer - Enterprise Products NVIDIASenior Research Engineer - Enterprise ProductsUs, WashingtonBuild and run agentic benchmarks (e.g., Terminal-Bench ) to measure algorithm quality, and turn results into calibration data and routing profiles. Experience designing or running LLM evaluations/benchmarks — ideally agentic ones — and drawing statistically sound conclusions from them.