Several years ago Schwinger proposed a physical mechanism for sonoluminesce
nce in terms of changes in the properties of the quantum-electrodynamic vac
uum state during collapse of the bubble. This mechanism is most often phras
ed in terms of changes in the Casimir energy (i.e., changes in the distribu
tion of zero-point energies) and has recently been the subject of considera
ble controversy. The present paper further develops this quantum-vacuum app
roach to sonoluminescence: We calculate Bogolubov coefficients relating the
QED vacuum states in the presence of a homogeneous medium of changing diel
ectric constant. In this way we derive an estimate for the spectrum, number
of photons, and total energy emitted. We emphasize the importance of rapid
spatio-temporal changes in refractive indices and the delicate sensitivity
of the emitted radiation to the precise dependence of the refractive index
as a function of wave number, pressure, temperature, and noble gas admixtu
re. Although the basic physics of the dynamical Casimir effect is a univers
al phenomenon of QED, specific and particular experimental features are enc
oded in the condensed matter physics controlling the details of the refract
ive index. This calculation places rather tight constraints on the possibil
ity of using the dynamical Casimir effect as an explanation for sonolumines
cence, and we are hopeful that this scenario will soon be amenable to direc
t experimental probes. In the following paper we discuss the technical comp
lications due to finite-size effects, but for reasons of clarity in this pa
per we confine our attention to bulk effects.