picoseconds

A picosecond (symbol ps) is a unit of time equal to one trillionth of a second (10^-12 s). It is a submultiple of the second in the International System of Units, derived from the SI prefix pico-.

In ultrafast science, picoseconds are used to quantify phenomena such as molecular vibrations, relaxation processes in solids and liquids, and carrier dynamics in semiconductors. One picosecond equals 1000 femtoseconds and 0.001 nanoseconds, illustrating its position on the spectrum of short time scales. Many laser pulses have durations in the picosecond range, while femtosecond pulses (10^-15 s) are shorter by several orders of magnitude.

Measuring picoseconds employs specialized techniques such as pump-probe spectroscopy, cross-correlation, autocorrelation, streak cameras, and optical sampling. These methods enable time-resolved investigations of fast electronic, vibrational, and chemical processes.

Light travels about 0.3 millimeters in vacuum per picosecond, a relation that helps intuition about timing in experiments. In materials, the effective distance light travels is shorter due to refractive index, but the correspondence remains a useful reference for understanding picosecond-scale events.

See also nanosecond, femtosecond, attosecond.