Thenumberandinitialpositionsofthebands
weredeterminedbycalculatingthesecondderivativeofthemassiffor
each spectrum(Fig. 3). Eachminimumindicatesthepositionofaband
(Fig. 3 a, b).Thepositionsaremanuallyreadattheminimumofeach
band.Itcanbenoticedthatforthearcheologicalcopal,theinternal
and externalsamplingCHstretchingregionspresentthesamenumber
and bandpositions.Thedifferentparametersareintroducedtothe
ASREL software:thebandspositions P areenteredaccordingtothe
second derivativeminima's values; W hasanarbitraryinitialvalueof
10 cm−1 (viablevalueforamolecularvibrator)andisconstrainedto
positivevalues, K hasaninitialvalueof0.5andisconfined between0
(Gaussian profile) and1(Lorentzianprofile), and finally A is just
limited topositivevalues. Concerningthe fitting procedure,itisbased
on aleastsquaresmethodwhichadjuststhebandparametersto fit
the experimentalspectrum.