page_title: Resonance ionization
section_title: Applications
hierarchical_section_title: Resonance ionization / Applications
caption_attribution_description: ARGONNE'S ULTRA-SENSITIVE TECHNIQUE FOR DETECTING TRACE AMOUNTS OF IMPURITIES ON MATERIAL SURFACES. ARGONNE SCIENTISTS HAVE DEVELOPED THE TECHNIQUE KNOWN AS SARISA (SURFACE ANALYSIS BY RESONANCE IONIZATION) IN ORDER TO DETECT TRACE AMOUNTS OF IMPURITIES ON MATERIAL SURFACES. THIS CAPABILITY IS IMPORTANT, PARTICULARLY IN THE MANUFACTURE OF SUPER-MINIATURE SEMICONDUCTORS. THIS METHOD OF MULTI-STEP EXCITATION AVOIDS THE IONIZATION OF BACKGROUND ATOMS, WHICH INTERFERES WITH IMPURITY DETECTION. For more information or additional images, please contact 202-586-5251.
context_page_description: Resonance ionization is a process in optical physics used to excite a specific atom beyond its ionization potential to form an ion using a beam of photons irradiated from a pulsed laser light. In resonance ionization, the absorption or emission properties of the emitted photons are not considered, rather only the resulting excited ions are mass-selected, detected and measured. Depending on the laser light source used, one electron can be removed from each atom so that resonance ionization produces an efficient selectivity in two ways: elemental selectivity in ionization and isotopic selectivity in measurement.
  During resonance ionization, an ion gun creates a cloud of atoms and molecules from a gas-phase sample surface and a tunable laser is used to fire a beam of photons at the cloud of particles emanating from the sample.
  An initial photon from this beam is absorbed by one of the sample atoms, exciting one of the atom's electrons to an intermediate excited state.
context_section_description: As an analytical technique, RIS is useful based on some of its working operations – they include extremely low detection limit so that mass of samples could be identified up to the order of 10⁻¹⁵, the extremely high sensitivity and elemental selectivity useful in micro- and trace analysis when coupled with mass spectrometers, and ability of the pulsed laser ion source to produce pure isobaric ion beams.
  A major advantage of using resonance ionization is that it is a highly selective ionization mode; it is able to target a single type of atom among a background of many types of atoms, even when said background atoms are much more abundant than the target atoms. In addition, resonance ionization incorporates the high selectivity that is desired in spectroscopy methods with ultrasensitivity, thus making resonance ionization useful when analyzing complex samples with several atomic components.
  Resonance ionization spectroscopy (RIS) thus has a wide range of research and industrial applications. These include characterizing the diffusion and chemical reaction of free atoms in a gas medium, solid state surface analysis using direct sampling, studying the degree of concentration variations in a dilute vapor, detecting the allowable limits of number of particles needed in a semiconductor device, and estimating the flux of solar neutrinos on Earth.
  Other uses include determining high-precision values for plutonium and uranium isotopes in a rapid fashion, investigating the atomic properties of technetium at the ultra trace level, and capturing the concurrent excitation of stable daughter atoms with the decay of their parent atoms as is the case for alpha particles, beta rays, and positrons.
  RIS is now in very common use in research facilities where the quick and quantitative determination of the elemental composition of materials is important.
  Pulsed laser light sources provide higher photon fluxes than continuous-wave lasers do, however the use of pulsed lasers currently limit vast applications of RIMS in two ways. One, photo ions are created only during short laser pulses, thus significantly reducing the duty cycle of pulsed resonance ionization mass spectrometers relative to their continuous-beam counterparts. Two, incessant drifts in laser pointing and pulse timing alongside jitters between pulses severely hamper chances of reproducibility.
  These issues affect the extent to which resonance ionization can be used to solve some of the challenges confronted by practical analysts today; even so, applications of RIMS are replete in various traditional and emerging disciplines such as cosmochemistry, medical research, environmental chemistry, geophysical sciences, nuclear physics, genome sequencing, and semiconductors.
caption: Surface analysis resonance ionization uses a multi-step excitation technique to avoid the interference of background atoms in detecting trace amounts of impurities on material surfaces. This ultra-sensitive technique is especially important in the manufacture of super-miniature semiconductors.
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