Final answer:
Fine structure in atomic spectra is related to the intrinsic spin of electrons and their interaction with the orbital magnetic field, causing the splitting of spectral lines into doublets. This quantum phenomenon was explained by Goudsmit and Uhlenbeck in 1925, providing key insights into electron behavior on a subatomic level.
Step-by-step explanation:
The student's question pertains to the concept of fine structure in atomic spectra, which involves a splitting of spectral lines into doublets due to the intrinsic magnetic field of electrons interacting with an orbital magnetic field. This splitting is observed even in the absence of an external magnetic field, a phenomenon explored and explained through the pioneering work of Sem Goudsmit and George Uhlenbeck in 1925. They proposed that electrons possess an intrinsic angular momentum, known as spin, which generates an intrinsic magnetic field. This spin interacts with the orbital magnetic field, leading to the energy differences that cause the fine structure in spectral lines.
Furthermore, this intrinsic spin is quantized in both magnitude and direction. When placed in a magnetic field, electrons exhibit two distinct spin states: spin up or spin down, each associated with different energies. This quantization results in the splitting of spectral lines into two close but separate lines, referred to as doublets. The presence of an external magnetic field can further affect these energies causing complex patterns such as Zeeman splitting, where lines can split into multiple components proportional to the strength of the applied field. This evidences a direct interaction between the moving charged electron and the magnetic field.