Femtosecond thermal modulation measurements of electron‐phonon relaxation in niobium

Thermal modulation measurements using 120 fs/620 nm laser pulses were performed on niobium films. The electron‐phonon relaxation time was found to be ultrafast and measured to be 360 fs, and the electron‐phonon coupling constant was estimated to be (17±3)×1017 W m−3 K−1.