Measurement apparatus and techniques for ultrashort events using electron photoemission with a superlinear photoemission active element

Measurement apparatus comprising:

• a) a target material exhibiting superlinear electron photoemission when irradiated,
• b) a source of prompt radiation pulses directed at said target and capable when absorbed by the target of raising electrons in the target from a first state to a second excited state at an energy level higher than that of said first state,
• c) a source of probe radiation pulses directed at said target and capable when absorbed by the target while electrons occupy said second excited state of raising said electrons to a third excited state wherein the electrons are capable of escaping from the target thereby changing the second excited state of the target,
• d) means coupled to the target for measuring its charge state thereby providing an indication of the pulse duration of the radiation pulses or the lifetime of the second excited state of the target material.

A method of measuring radiation pulse parameters or the excited state lifetimes of a target material, comprising the steps:

• a) provided a target material exhibiting superliner electron photoemmision when irradiated,
• b) impinging on the target a pulse of prompt radiation so as to raise electrons from a ground state to a first higher excited state,
• c) while electrons occupy the excited first state, impinging on the target a pulse of probe radiation capable of raising electrons occupying the excited first state to its vacuum state thereby causing emission of electrons from the target causing the target to become more positively charged to a higher level,
• d) measuring said higher level assumed by the target as an indication of the pulse widths of the impinging radiation or of the lifetime of the first excited states.

Measurement apparatus comprising:

• a) a sample material exhibiting non-linear electron photoemission when irradiated,
• b) a source of prompt radiation pulses directed at said sample and capable when absorbed by the sample of raising electrons in the sample from a ground state to a first excited state at an energy level higher than that of said ground state,
• c) a source of probe radiation pulses directed at said sample and capable when absorbed by the sample while electrons occupy said first excited state of raising said electrons to a second excited state wherein the electrons are capable of escaping from the sample thereby changing the charged state of the sample in a positive direction,
• d) means coupled to the sample for measuring its charge state thereby providing an indication of parameters of the radiation pulses or properties of the sample material.

A method of measuring radiation pulse parameters or properties of a sample material, comprising the steps:

• a) providing a sample material exhibiting non-linear electron photoemission when irradiated,
• b) impinging on the sample a pulse of prompt radiation so as to raise electrons from a ground state to a higher first excited state,
• c) while electrons occupy the first excited state, impinging on the sample a pulse of probe radiation capable of raising electrons occupying the first excited state to its vacuum state thereby causing emission of electrons from the sample causing the sample to lose negative charge,
• d) thereafter measuring the charge assumed by the sample as an indication of parameters of the impinging radiation or of the lifetime of the first excited states.