Attosecond science involves the generation and measurement of extremely short light pulses, on the order of attoseconds (10^-18 seconds), to study ultrafast processes in atoms and molecules. These pulses, first produced in 2001, enable the observation of events such as electron motion and molecular dynamics on timescales previously unobservable. The shortest pulses reported have durations of about 53 attoseconds, allowing scientists to probe phenomena like photoionisation delays and molecular dissociation. High harmonic generation (HHG) is a key method for producing attosecond pulses. It involves the interaction of an intense laser field with an atom, causing an electron to be ionised, accelerated, and then recombine with the ion, emitting a photon. This process, described by a three-step model, can be understood classically and quantum mechanically. The quantum mechanical approach involves the interference of the electron's wavefunction, leading to the emission of a coherent attosecond pulse. The measurement of attosecond pulses is achieved through techniques such as RABBIT (Reconstruction of attosecond beating by interference of two-photon transitions), which uses the interference of photoelectron spectra to determine the phase and shape of the pulse. Another method, the attosecond streak camera, uses the infrared laser field to deflect electrons, enabling the temporal characterization of the pulse. Applications of attosecond science include the study of photoionisation delays, where the time taken to remove an electron from an atom or surface is measured. Experiments have shown that deeper-bound electrons take longer to be removed, with delays on the order of tens of attoseconds. Additionally, attosecond pulses are used in transient absorption spectroscopy to observe electronic transitions and charge states in molecules, providing insights into molecular dynamics. The field of attosecond science continues to evolve, with ongoing research into improving pulse generation, measurement techniques, and applications in areas such as molecular dynamics and quantum chemistry. The ability to observe processes on the attosecond timescale opens new avenues for understanding fundamental physical and chemical phenomena.Attosecond science involves the generation and measurement of extremely short light pulses, on the order of attoseconds (10^-18 seconds), to study ultrafast processes in atoms and molecules. These pulses, first produced in 2001, enable the observation of events such as electron motion and molecular dynamics on timescales previously unobservable. The shortest pulses reported have durations of about 53 attoseconds, allowing scientists to probe phenomena like photoionisation delays and molecular dissociation. High harmonic generation (HHG) is a key method for producing attosecond pulses. It involves the interaction of an intense laser field with an atom, causing an electron to be ionised, accelerated, and then recombine with the ion, emitting a photon. This process, described by a three-step model, can be understood classically and quantum mechanically. The quantum mechanical approach involves the interference of the electron's wavefunction, leading to the emission of a coherent attosecond pulse. The measurement of attosecond pulses is achieved through techniques such as RABBIT (Reconstruction of attosecond beating by interference of two-photon transitions), which uses the interference of photoelectron spectra to determine the phase and shape of the pulse. Another method, the attosecond streak camera, uses the infrared laser field to deflect electrons, enabling the temporal characterization of the pulse. Applications of attosecond science include the study of photoionisation delays, where the time taken to remove an electron from an atom or surface is measured. Experiments have shown that deeper-bound electrons take longer to be removed, with delays on the order of tens of attoseconds. Additionally, attosecond pulses are used in transient absorption spectroscopy to observe electronic transitions and charge states in molecules, providing insights into molecular dynamics. The field of attosecond science continues to evolve, with ongoing research into improving pulse generation, measurement techniques, and applications in areas such as molecular dynamics and quantum chemistry. The ability to observe processes on the attosecond timescale opens new avenues for understanding fundamental physical and chemical phenomena.