Acknowledgments [1] J.D. Cramer and H.C. Britt, Nucl. Sci. Eng. 41 , 177 (1970). [2] H.C. Britt and J.B. Wilhelmy, Nucl. Sci. Eng. 72 , 222 (1979). [3] M. Petit et al. , Nucl. Phys. A 735 , 347 (2004). [4] S. Boyer et al. , Nucl. Phys. A 775 , 175 (2006). 10 The authors are grateful to Drs. A. Iwamoto, K. Nishio, S. Hashimoto and Y. Aritomo for fruitful discussions. Present study is the result of “Development of a Novel Technique for Measurement of Nuclear Data Influencing the Design of Advanced Fast Reactors” entrusted to Japan Atomic Energy Agency (JAEA) by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT). It must be also noted that we use a standard Hauser-Feshbach calculation using models and parameters adjusted to reproduce neutron cross sections, but the results may have some dependence on them. Such a dependence, however, is expected also to be small in the surrogate ratio method, since many factors in models and parameters can cancel out in the ratio quantities. condition, namely, J π by J π convergence of the branching ratios and their coincidence to the neutron reaction ratio, defined in this work. Furthermore, it is important to select a pair of nuclei, one of which is the reference nucleus, having similar properties so that the excitation spectra of various J π states can be considered almost equivalent. These conditions are the basis for the surrogate ratio method to work. Furthermore, it was shown to be rather robust even breakup reaction occurs. This was shown again without assuming any breakup reaction mechanisms. Altogether, the surrogate ratio method was proved to be a useful method to determine neutron cross sections for which the direct measurements using neutrons are not possible. Generally speaking, however, application of the surrogate method must be done with a caution. It will be very sensitive to the spin and parity of the decaying nucleus at low energies since transitions to discrete levels, which differ nucleus to nucleus, occupy a dominant part of the decay branch there. This is the reason why the weak Weisskopf-Ewing condition tends to be violated at lower energies.