of R-CHI groups and the formation of C,Hp, ions is observed. This situation might be expected to prevail when the charge carrying fragment has a sufficiently long unbranched chain to allow it-provided the alkane formed is not methane c.f. (M-15) ion in the iso-alkane series. In addition, this mechanism lends itself to a specific prediction when suitable deuterated materials are available. We are a t present investigating this aspect of the fragmentation mechanism. is shown below in which hydrogen transfer from a secondary position takes place to form a cis 1,2-dialkylcyclohexane ion and a n alkane. The metastable peaks correspond to the loss
ACKNOWLEDGMENT
We thank Drs. H. K. Schnoes, and R. T. Aplin for carefully reviewing aspects of the manuscript. The work described here was sponsored in part by the National Aeronautics and Space Administration and in part by the U.S. Atomic Energy Commission. RECEIVED for review April 3, 1968. Accepted May 22, 1968
Computation of Lithium-Drifted Germanium Detector Peak Areas for Activation Analysis and Gamma Ray Spectrometry Herbert P. Yule Activation Analysis Research Laboratory, Texas A & M Unioersity, College Station, Texas 77843 This paper reports results of studies of net full energy peak area computation methods for activation analysis and gamma ray spectrometry. Using a computer routine to search for any and all peaks in the spectrum, peak boundary channels are located by studying the behavior of a smoothed spectrum and a smoothed first derivative spectrum, each formed from the original spectrum. Net peak areas are computed from that portion of the spectrum enclosed by the peak boundary channels, overcoming changes in peak shape due to resolution losses and to other causes. This method gives accurate results for activation analysis, decay curve resolution, and other peak intensity studies.
QUANTITATIVE RESULTS obtained from Ge(Li) detector peak area measurements by Covell’s ( I ) method suggest that inaccuracies may occur at moderate or high counting rates (>-20% dead time) (2, 3). In the present study, early experiments indicated that peak areas are too low at high counting rates. The primary purpose of this study has been t o determine whether Covell’s method of computing peak areas could be successfully applied t o Ge(Li) detector data, and to find a means of accurate peak area computation at moderate and high counting rates, if Covell’s method were shown t o be inaccurate. In a preliminary experiment, sources of Ig8Au and 6oCo were counted individually and together. The counting times
in each instance were 25 minutes (live time), and the approximate percentage dead times were 22 for 6oCo, 0.5 for 198Au, and 22 for the two sources together. A synthetic spectrum was computed by summing the spectra of the individual sources, including a small decay correction (
