Irene Joliot-Curie, along with her husband Frédéric Joliot, conducted groundbreaking experiments in nuclear physics. In their famous experiment leading to the discovery of artificial radioactivity, the target substance they used was aluminum.

Here's how the experiment worked:

1. Alpha Particle Bombardment: They bombarded aluminum with alpha particles emitted from polonium.

2. Nuclear Reaction: This bombardment caused a nuclear reaction, where an alpha particle (helium nucleus) was absorbed by the aluminum nucleus.

3. Production of Phosphorus: The resulting nucleus was that of phosphorus-30, an unstable isotope.

4. Artificial Radioactivity: Phosphorus-30 decayed through beta particle emission, resulting in silicon-30. This decay process exhibited artificial radioactivity, meaning it was induced by the bombardment process and not naturally occurring.

Their discovery of artificial radioactivity had profound implications for nuclear physics and opened doors to further research in this field.