A Computer Program for Simulating First-Order Electron Spin Resonance Spectra A computer program has been written in Fortran IVG to simulate first-order electron spin resonance spectra. The program requires approximately 108 kbytes, and on the West Virginia University IBM-360175 takes between 7 see and 8 min to execute, depending on the options called. The program will accommodate up to nine individual radical spectra, up to 1000 lines per spectrum, and has a resolution of 25 mG a t +lo G scan range (with correspondingly. 250 mG a t +I00 G, and 2.5 G at +I000 G scans). Output from the program consists of a plot (adjustable t o s u i t any scan range or esr spectrometer chart size, and with an adjustable spectrum intensity factor) and/or a numerical listing of relative intensities as a function of gauss scale. The numerical listing provides a f25% overscan for any selected spectrum to allow detection of lines that lie in the extreme wings of a spectrum and are not seen by the spectrometer and/ or plotter output a t that particular scan setting. Options included in the program are as follows. Spectra presentation as Lorentzian or Gaussian absorption curves, Lorentzian or Gaussian first derivative CUNeS, Lorentzian or Gaussian second derivative curves, or a " s t i c k spectrum presentation. It is also possible to modify the pmgram so that, for example, a basically first derivative presentation contains a 10% admixture of the second derivative curve. The systematic increase in line width for any of the nine radical spectra is possible, up to a maximum of nine increments per radical (and thus an overall total of 81 plots). This option may be easily modified to allow a systematic change in hyperfine constant for one set of nucleii in any one radical instead of the line width. The numerical output from the Droeram lists the relative intensities for the first initial line width selected for each radical being investi. gated. A further option is the addition of up to three individual spectra to form a composite plot. Included in the option is the ability to shift any, or all, spectra upfield or downfield (to compensate for different G-values), and variation in relative intensities of one spectrum relative to the others to allow small contributions of one species to the whole to be assessed. Another option included is the addition of asingle peak to the spectrum, or spectra, to reproduce signals resulting from the formation of V or K centers in crystalline solids, peaks from chemical radical-generators such as organic peroxides or metal ionlhydmxyl systems, peaks attributable to trapped electrons or COz- anions in glassy or polycrystalline matrices, or peaks generated by photolysis or radiolysis of esr cell envelopes. Included with this option is the ability to vary the intensity of this single peak relative to the underlying spectrum, to alter the line width independently of the underlying spectrum, and to shift the peak upfield/downfield relative t o the center of the underlying spectrum. Input to the program consists primarily of the number of sets of equivalent nucleii in any particular radical, the line width of the radical spectrum (assumed constant for each set in any one radical), and then for each set of equivalent nucleii; the number of nucleii, the nuclear spin, and the hyperfine constant. The pmgram itself will generate the required set of intensity factors (a function of nuclear spin and number of nucleii), and the program will handle up to twelve nucleii of spin one-half, six nucleii of spin one, and one nucleus of spin up t o eleven-halves. Other combinations can be easily accommodated by addition to the program. Additional data inputs are necessary far the optional parameters described above. Reasonably liberal comment cards are included describing data-input formats and other required factors. The author will be pleased to supply a listing of the program to interested persons, but he regrets that he cannot supply duplicate decks. A. Campbell Ling West Virginia university Morgantown, 26506
174
/
Journal ot Chemical Education
