D ▁correlation ▁analysis ▁gained ▁w ides p read ▁use . ▁Altern ative ▁techniques ▁that ▁were ▁simpler ▁to ▁calculate , ▁for ▁example ▁the ▁dis relation ▁spectrum , ▁were ▁also ▁developed ▁simultaneously . ▁Because ▁of ▁its ▁computational ▁efficiency ▁and ▁simplicity , ▁the ▁Hil bert ▁transform ▁is ▁now ad ays ▁used ▁for ▁the ▁calculation ▁of ▁the ▁ 2 D ▁spect ra . ▁To ▁date , ▁ 2 D ▁correlation ▁analysis ▁is ▁used ▁for ▁the ▁interpretation ▁of ▁many ▁types ▁of ▁spect ro scop ic ▁data ▁( including ▁X R F , ▁U V / VIS ▁spect ro sc opy , ▁flu ores c ence , ▁inf ra red , ▁and ▁Ram an ▁spect ra ), ▁although ▁its ▁application ▁is ▁not ▁limited ▁to ▁spect ro sc opy . ▁ ▁Properties ▁of ▁ 2 D ▁correlation ▁analysis ▁▁ 2 D ▁correlation ▁analysis ▁is ▁frequently ▁used ▁for ▁its ▁main ▁advantage : ▁increasing ▁the ▁spectral ▁resolution ▁by ▁spread ing ▁over la pping ▁pe aks ▁over ▁two ▁dimensions ▁and ▁as ▁a ▁result ▁simpl ification ▁of ▁the ▁interpretation ▁of ▁one - dimensional ▁spect ra ▁that ▁are ▁otherwise ▁vis ually ▁ind ist ingu ish able ▁from ▁each ▁other . ▁Further ▁advantages ▁are ▁its ▁ease ▁of ▁application ▁and ▁the ▁possibility ▁to ▁make ▁the ▁distinction ▁between ▁band ▁sh ifts ▁and ▁band ▁overlap . ▁Each ▁type ▁of ▁spectral ▁event , ▁band ▁sh ifting , ▁over la pping ▁bands ▁of ▁which ▁the ▁intensity ▁changes ▁in ▁the ▁opposite ▁direction , ▁band ▁bro aden ing , ▁bas eline ▁change , ▁etc . ▁has ▁a ▁particular ▁ 2 D ▁pattern .