Reciprocal centimetres

It is, however, customary to quote absorption bands in units of wavenumber (v) which are expressed in reciprocal centimetres, cm-1. In some instances wavelengths (2) measured in micrometres (/um) are also used. The relationship... 

In some literature accounts, the term wave number (v) is used. This is the number of wavelengths per centimetre, and consequently wave number has units of reciprocal centimetres (cm4). 

The term ionisation potential (IP) refers to an intensive property of a single atom or ion in the gas phase. Measured spectroscopically, it is equal to the energy difference between En+ and E(n+1)+ (n = 0,1,2,...), both species being in their respective ground states. Loosely, but perhaps more usefully, the ionisation potential of an atom or ion is equal to the energy required to remove its outermost electron. The ionisation potential is usually measured in electron volts (eV), although it is sometimes tabulated in the spectroscopic unit of reciprocal centimetres (cm-1) leV s 8066 cm-1. 

Some spectra are recorded on a wavenumber scale, which is inversely proportional to wavelength. The most common wavenumber unit is the reciprocal centimetre, which is related to wavelength units as follows ... 

Other units that you may encounter, especially in connection with spectroscopic data are for wavelength. Angstrom (A 1 A = 0.1 nm) for energy, electron volt (eV 1 eV = 96.5 k mol- ) for wavenumber (v = X- ), reciprocal centimetre (cm ). Sometimes cm is employed as though it were an energy unit, but this is only a convenient shorthand. Some organic photochemists still use calorie (cal 1 cal = 4.18 ) as their preferred energy unit. 

Other terms used extensively in spectroscopy are the wavenumber and the frequency. The wavenumber is defined as the number of waves per unit of length (usually quoted in units of reciprocal centimetres (cm4 where 1 cm = 10 2 m) and is the reciprocal of the wavelength in centimetres, i.e. HX. The use of wavenumber is usually confined to infrared spectroscopy The frequency is defined as the number of waves emitted from a source per second the unit of frequency is the hertz (Hz 1 Hz = 1 wave per second), and the symbol for it is v (the Greek letter nu ). 

The x-axis, the wavelength of the radiation, is given in wavenumbers (v) and expressed in reciprocal centimetres (cm-1). You may still see some spectra from old instruments using microns (ji, equivalent to the SI unit micrometres , /an, at 1 x 10-6m) for wavelength the conversion is given by eqn [28.2] ... 

When infrared spectra are recorded, the frequency [in reciprocal centimetres (cm-1)] or, less often, the wavelength [in microns (p)], [in microns (p)] is plotted as the abscissa, and the per cent absorbance or per cent transmittance is plotted as the ordinate. 

The unit of wavelength commonly used in visible or ultra-violet spectroscopy is the angstrom unit, A, or the millimicron, m, equal to 10 A. Sometimes the wave number, v — 1/A, is also used. The unit of wave number is the reciprocal centimetre, cm"1. 

A frequency factor (in Arrhenius cm reciprocal centimetre (wavenumber)... 

The wavelength of the sodium D line is 589.0 nm. What is the wavelength in angstroms What is the wavenumber in reciprocal centimetres and the frequency in reciprocal seconds ... 

A wide variety of energy units is used in the literature connected with light. A common nonstandard unit of energy is the electron volt (eV), but spectroscopists more often use reciprocal centimetres (cm ). In wavelength designations, a common nonstandard unit is the Angstrom (A). 

The eigenvalues of the secular equation yield the frequencies of the normal modes, which are usually expressed as wavenumbers, v, preferentially in reciprocal centimetres, cm by dividing the frequency by the speed of light, c. 

Wavenumber is the reciprocal of wavelength convenient (non-SI) units are reciprocal centimetres , cm ... 

The unit of wavelength, the micron (//, f.i 10 cm), and the unit of so-called frequency or wave-number, the reciprocal centimetre (cm i), are interchangeable [wavelength (//) --- 10 wave-number (cm )], and because it has not been agreed internationally which to adopt as standard nomenclature, analysts must be familiar with both. 

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