Short pulsewidth repetition rate nanosecond transient absorption spectrometer

A high-sensitivity nanosecond to millisecond transient absorption spectrometer for measurements of miniscule signals under low excitation intensities, comprising:

• an excitation source generating a frequency greater than 100 Hz, pulsewidth less than 5 ns excitation pulse for exciting a light absorbing sample;
• a probe light source for generating a photon flux probe light beam producing an average irradiance greater than 1 μW m−2 nm−1 for measuring the transient absorption spectrum of the sample by monitoring transmission signals of the probe light beam before and after excitation by the excitation source;
• a DC-coupled detector operable to measure light for enabling synchronous measurement of both the transmission of the probe light beam in an absence of the excitation pulse and the change in transmission of the probe light beam between a signal with the excitation pulse present and a signal in the absence of the excitation pulse;
• and
• a digital oscilloscope with a trigger rearm time capable of collecting every trigger event at high frequencies including 1 MHz, for enabling sequential noise subtraction protocols.

A method of measuring miniscule signals under low excitation intensities using a high-sensitivity nanosecond to millisecond transient absorption spectrometer, the method comprising:

• exciting a light absorbing sample using excitation pulses each having a frequency greater than 100 Hz and a pulsewidth less than 5 ns;
• after a delay of each excitation pulse, transmitting a probe light beam to the light absorbing sample, the probe light beam having a photon flux, producing an average irradiance greater than 1 W m−2 nm−1;
• collecting the transmitted probe light beam signals using a detector, the detector being a DC-coupled detector operable to measure light for enabling sequential switching of an AC- and DC-coupled detection scheme;
• recording a change in the transmission AT of the probe light beam between the collected signal with the excitation pulse present and the signal in an absence of the excitation signal using a digital oscilloscope;
• recording a steady-state transmission T of the probe light beam in the absence of the excitation pulse using the digital oscilloscope;
• and
• generating a transient absorption spectrum by calculating transient absorption signals using ΔT/T,
• wherein the digital oscilloscope having a trigger rearm time capable of collecting every trigger event at high frequencies including 1 MHz, thereby enabling sequential noise subtraction protocols.