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Lifetimes of the 2 $$_1^{+}$$ , 4 $$_1^{+}$$ , 7 $$_2^{-}$$ , 10 $$_2^{+}$$ , 12 $$_2^{+}$$ , and 14 $$_1^{+}$$ states in $$^{138}$$ Nd populated via the $$^{123}$$ Sb( $$^{19}$$ F, 4n) $$^{138}$$ Nd fusion–evaporation reaction were measured with the recoil distance Doppler shift technique in combination with the differential decay curve method. The $$B(E2; 2_{1}^{+} \rightarrow 0_{1}^{+})$$ value fit well with the systematic trend in the Nd isotope chain and Grodzins rule, which proved that $$^{138}$$ Nd is a transitional nucleus.

A new development of indirect gating case in the differential decay curve method used for lifetime measurement has been introduced. The gate region was extended from partial shifted peak to both shifted and unshifted components. The statistics of flight and stop peaks in gating spectra was improved obviously. The reliability of this change has been tested by reanalysing the lifetime of $$2^{+}$$ state in $$^{134} \hbox {Ce}$$ . The result of 32.2(33) ps was fit well with the previous published values within the experimental uncertainty. The developed method was also used to analyse the lifetime of $$2_1^{+}$$ state in $$^{138} \hbox {Nd}$$ .