Yenching University (1926–1937) After completing his doctorate, Hsieh returned to China and was appointed professor of physics at
Yenching University in
Beijing. He became the first Chinese chairman of the Department of Physics, succeeding American physicist Paul A. Anderson. Their measurements revealed discrepancies of approximately 3% between experimental results and theoretical predictions based on the
Dirac equation. Significantly, Houston and Hsieh concluded that "the discrepancy may lie in the neglect of the radiation reaction in the calculation of the energy levels," an early identification of what would later be understood as the self-energy correction underlying the
Lamb shift. The phenomenon was later definitively measured by
Willis Lamb and Robert Retherford in 1947, for which Lamb received the
Nobel Prize in Physics in 1955. Nobel laureate
Yang Chen-Ning later wrote that the Houston-Hsieh work was notable for its prescient identification of quantum electrodynamic effects.
Wartime service at Xiamen University (1937–1946) Following the outbreak of the
Second Sino-Japanese War in July 1937, Hsieh and his family left Beijing. After briefly teaching at
Hunan University, he accepted an invitation in November 1939 from
Sa Bendong, president of
Xiamen University, to join the institution as professor of physics. At the time, Xiamen University had relocated to
Changting, Fujian Province, to escape Japanese occupation. At Changting, Hsieh maintained physics education under austere wartime conditions, building machine shops and laboratories despite resource shortages. He played a role in maintaining academic standards during one of the most turbulent periods in modern Chinese history. After Japan's surrender in 1945, Xiamen University returned to its original coastal campus, where Hsieh continued teaching until his departure for the Philippines. ==Career in the Philippines (1950–1968)==