The two-photon interband electron transitions in a silicon layer directly u
nderneath the Si(111)-SiO2 interface in the vicinity of the E-2 critical po
int (CP) are probed by optical second-harmonic (SH) spectroscopy. The combi
nation of the SH phase and intensity spectroscopy allows the complete decon
volution of the spectral behavior of the amplitude and phase of the quadrat
ic susceptibility chi((2)) near the E-2 critical point of silicon. (C) 2000
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