On the Traversal Time of Barriers

Fifty years ago Hartman studied the barrier transmission time of wave packets, inspired by tunneling experiments across thin insulating layers of that era. He calculated faster than light (FTL) propagation for opaque barriers, along with a transmission time independent of barrier length, known as the Hartman effect. Analog tunneling experiments with microwaves and infrared light, conducted thirty years later, confirmed this FTL wave packet velocity. Recently, claims arose of observing the conjectured zero time of electron tunneling in ionizing helium within the barrier. This calculated and measured short tunneling time originates at the barrier front and is universal for both elastic and electromagnetic fields. Notably, the delay time for reflected and transmitted waves at symmetric barriers remains identical. Several theoretical physicists have predicted these unusual tunneling process characteristics; however, many in the physics community dispute the FTL signal velocity interpretation of experimental tunneling results, preferring a calculated luminal front velocity. Notably, Brillouin argued that front velocity corresponds to the group velocity of wave packets in physical signals with finite frequency bandwidths. Some studies equate barriers to cavities, suggesting the observed tunneling time reflects cavity lifetime. This paper discusses the continuing misleading interpretations widespread in journals and textbooks to date.