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2006–present. Number built. 1,000+ [4] Developed from. Lockheed Martin X-35. The Lockheed Martin F-35 Lightning II is an American family of single-seat, single-engine, stealth multirole combat aircraft designed for air superiority and strike missions; it also has electronic warfare and intelligence, surveillance, and reconnaissance capabilities.
Produced. 1973–1974, 1983–1988. Number built. 104 [a] The Rockwell B-1 Lancer [b] is a supersonic variable-sweep wing, heavy bomber used by the United States Air Force. It has been nicknamed the "Bone" (from "B-One"). [2] [3] It is one of the Air Force's three strategic bombers, along with the B-2 Spirit and the B-52 Stratofortress, as of 2024.
- Conceptual Introduction
- History
- Michelson Interferometer
- Measuring and Processing The Interferogram
- Advantages
- Motivation
- Components
- Spectral Range
- Applications
- See Also
The goal of absorption spectroscopy techniques (FTIR, ultraviolet-visible ("UV-vis") spectroscopy, etc.) is to measure how much light a sample absorbs at each wavelength. The most straightforward way to do this, the "dispersive spectroscopy" technique, is to shine a monochromatic light beam at a sample, measure how much of the light is absorbed, an...
The first low-cost spectrophotometer capable of recording an infrared spectrum was the Perkin-Elmer Infracord produced in 1957. This instrument covered the wavelength range from 2.5 μm to 15 μm (wavenumber range 4,000 cm−1 to 660 cm−1). The lower wavelength limit was chosen to encompass the highest known vibration frequency due to a fundamental mol...
In a Michelson interferometer adapted for FTIR, light from the polychromatic infrared source, approximately a black-body radiator, is collimated and directed to a beam splitter. Ideally 50% of the light is refracted towards the fixed mirror and 50% is transmitted towards the moving mirror. Light is reflected from the two mirrors back to the beam sp...
The interferogram has to be measured from zero path difference to a maximum length that depends on the resolution required. In practice the scan can be on either side of zero resulting in a double-sided interferogram. Mechanical design limitations may mean that for the highest resolution the scan runs to the maximum OPD on one side of zero only. Th...
There are three principal advantages for an FT spectrometer compared to a scanning (dispersive) spectrometer. 1. The multiplex or Fellgett's advantage. This arises from the fact that information from all wavelengths is collected simultaneously. It results in a higher signal-to-noise ratio for a given scan-time for observations limited by a fixed de...
FTIR is a method of measuring infrared absorption and emission spectra. For a discussion of why people measure infrared absorption and emission spectra, i.e. why and how substances absorb and emit infrared light, see the article: Infrared spectroscopy.
IR sources
FTIR spectrometers are mostly used for measurements in the mid and near IR regions. For the mid-IR region, 2−25 μm (5,000–400 cm−1), the most common source is a silicon carbide (SiC) element heated to about 1,200 K (930 °C; 1,700 °F) (Globar). The output is similar to a blackbody. Shorter wavelengths of the near-IR, 1−2.5 μm (10,000–4,000 cm−1), require a higher temperature source, typically a tungsten-halogen lamp. The long wavelength output of these is limited to about 5 μm (2,000 cm−1) by...
Detectors
Far-IR spectrometers commonly use pyroelectric detectors that respond to changes in temperature as the intensity of IR radiation falling on them varies. The sensitive elements in these detectors are either deuterated triglycine sulfate (DTGS) or lithium tantalate (LiTaO3). These detectors operate at ambient temperatures and provide adequate sensitivity for most routine applications. To achieve the best sensitivity the time for a scan is typically a few seconds. Cooled photoelectric detectors...
Beam splitter
An ideal beam-splitter transmits and reflects 50% of the incident radiation. However, as any material has a limited range of optical transmittance, several beam-splitters may be used interchangeably to cover a wide spectral range. For the mid-IR region the beamsplitter is usually made of KBr with a germanium-based coating that makes it semi-reflective. KBr absorbs strongly at wavelengths beyond 25 μm (400 cm−1) so CsI or KRS-5 are sometimes used to extend the range to about 50 μm (200 cm−1)....
Far-infrared
The first FTIR spectrometers were developed for far-infrared range. The reason for this has to do with the mechanical tolerance needed for good optical performance, which is related to the wavelength of the light being used. For the relatively long wavelengths of the far infrared, ~10 μm tolerances are adequate, whereas for the rock-salt region tolerances have to be better than 1 μm. A typical instrument was the cube interferometer developed at the NPL and marketed by Grubb Parsons. It used a...
Mid-infrared
With the advent of cheap microcomputers it became possible to have a computer dedicated to controlling the spectrometer, collecting the data, doing the Fourier transform and presenting the spectrum. This provided the impetus for the development of FTIR spectrometers for the rock-salt region. The problems of manufacturing ultra-high precision optical and mechanical components had to be solved. A wide range of instruments are now available commercially. Although instrument design has become mor...
Near-infrared
The near-infrared region spans the wavelength range between the rock-salt region and the start of the visible region at about 750 nm. Overtones of fundamental vibrations can be observed in this region. It is used mainly in industrial applications such as process control and chemical imaging.
FTIR can be used in all applications where a dispersive spectrometer was used in the past (see external links). In addition, the improved sensitivity and speed have opened up new areas of application. Spectra can be measured in situations where very little energy reaches the detector aaurier transform infrared spectroscopy is used in geology, chemi...
Number built. 598 as of 30 April 2024 [update] [4] The Airbus A350 is a long-range, wide-body twin-engine airliner developed and produced by Airbus . The initial A350 design proposed by Airbus in 2004, in response to the Boeing 787 Dreamliner, would have been a development of the Airbus A330 with composite wings and new engines.
Barry Bonds holds the Major League Baseball home run record with 762. [a] He passed Hank Aaron, who hit 755, on August 7, 2007. The only other players to have hit 700 or more are Babe Ruth with 714, and Albert Pujols with 703. Alex Rodriguez (696), Willie Mays (660), Ken Griffey Jr. (630), Jim Thome (612), and Sammy Sosa (609) are the only ...
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