resins, but more recently has referred specifically to gases in low-temperature solids. A typical matrix isolation experiment involves a guest sample being diluted in the gas phase with the host material, usually a noble gas or nitrogen. This mixture is then deposited on a window that is cooled to below the melting point of the host gas. The sample may then be studied using various spectroscopic
procedures.
Experimental setup
Apparatus for transmission measurements
The transparent window, on to which the sample is deposited, is usually cooled using a compressed
, may be used as the host material so that the reaction of the host with the guest species may be studied.
Using the matrix isolation technique, short-lived, highly-reactive species such as
spectroscopic means. For example, the solid noble gas krypton can be used to form an inert matrix within which a reactive F3− ion can sit in chemical isolation.[1] The reactive species can either be generated outside (before deposition) the apparatus and then be condensed, inside the matrix (after deposition) by irradiating or heating a precursor, or by bringing together two reactants on the growing matrix surface. For the deposition of two species it can be crucial to control the contact time and temperature. In twin jet deposition the two species have a much shorter contact time (and lower temperature) than in merged jet. With concentric jet the contact time is adjustable.[2]
Different deposition techniques
Spectroscopy
Within the host matrix, the
quantum states
are populated.
Especially
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.[3] This is especially useful for the validation of simulated infrared spectra that can be obtained from computational chemistry.[4]
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.[5] 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
laser-vaporization in matrix isolation spectroscopy rose in popularity due to its ability to generate transients involving metals, alloys and semi-conductor molecules and clusters.[6]
