  We propose to use spectator particle yield ratios to probe the configuration
of $\alpha$ clusters in $^{12}$C and $^{16}$O by their collisions at RHIC and
LHC energies. The idea is illustrated based on initial density distributions
with various $\alpha$-cluster configurations generated by a microscopic cluster
model, and without $\alpha$ clusters from mean-field calculations. The
multifragmentation of the spectator matter produces more spectator light nuclei
including $\alpha$ clusters in collisions of nuclei with chain structure of
$\alpha$ clusters, compared to those of nuclei with a more compact structure.
The yield ratio of free spectator neutrons to spectator particles with
mass-to-charge ratio $A/Z=2$ scaled by their masses can be practically measured
by the zero-degree calorimeter (ZDC) at RHIC and LHC, serving as a clean probe
free from modeling the complicated dynamics at midrapidities.
