merged jet. With concentric jet the contact time is adjustable. Spectroscopy Within the host matrix, the rotation and translation of the guest particle is usually inhibited. Therefore, the matrix isolation technique may be used to simulate a spectrum of a species in the gas phase without rotational and translational interference. The low temperatures also help to produce simpler spectra, since only the lower electronic and vibrational quantum states are populated. Especially infrared (IR) spectroscopy, which is used to investigate molecular vibration, benefits from the matrix isolation technique. For example, in the gas-phase IR spectrum of fluoroethane some spectral regions are very difficult to interpret, as vibrational quantum states heavily overlap with multiple rotational-vibrational quantum states. When fluoroethane is isolated in argon or neon matrices at low temperatures, the rotation of the fluoroethane molecule is inhibited. Because rotational-vibrational quantum states are quenched in the matrix isolation IR spectrum of fluoroethane, all vibrational quantum states can be identified. This is especially useful for the validation of simulated infrared spectra that can be obtained from computational chemistry. History Matrix isolation has its origins in the first half of the 20th century with the experiments by photo-chemists and physicists freezing samples in liquefied gases. The earliest isolation experiments involved the freezing of species in transparent, low temperature organic glasses, such as EPA (ether/isopentane/ethanol 5:5:2). The modern matrix isolation technique was developed extensively during the 1950s, in particular by George C. Pimentel. He initially used higher-boiling inert gases like xenon and nitrogen as the host material, and is often said to be the "father of matrix isolation". Laser vaporization in matrix isolation spectroscopy was first brought about in 1969 by Schaeffer and Pearson using a yttrium aluminum garnet (YAG) laser to vaporize carbon which reacted with hydrogen to produce acetylene. They also showed that laser-vaporized boron would react with HCl to create BCl. In the 1970s, Koerner von Gustorf's lab used the technique to produce free metal atoms which were then deposited with organic substrates for use in organometallic chemistry. Spectroscopic studies were done on reactive intermediates in around the early 1980s by Bell Labs. They used laser-induced fluorescence to characterize multiple molecules like SnBi and SiC. Smalley's group employed the use of this method with time-of-flight mass spectrometry by analyzing Al clusters. With the work of chemists like these, laser-vaporization in matrix isolation spectroscopy rose in popularity due to its ability to generate transients