Measuring the rotational temperature and pump intensity in molecular alignment experiments via high harmonic...

Area of Science:

• * Ultrafast laser science and molecular dynamics.
• * Quantum optics and spectroscopy.
• * Laser-matter interactions.

Background:

• * Laser-induced molecular alignment is a powerful technique for studying molecular dynamics.
• * Accurately determining experimental parameters like rotational temperature and laser intensity is crucial for reliable results.
• * Time-resolved high harmonic spectroscopy (HHS) offers a sensitive probe of molecular behavior.

Purpose of the Study:

• * To develop and demonstrate a novel method for simultaneous measurement of rotational temperature and pump intensity.
• * To utilize the time-resolved high harmonic spectroscopy (HHS) technique for this diagnostic purpose.
• * To validate the method's accuracy and robustness across different conditions and molecules.

Main Methods:

• * Analyzing the timing of local extrema (minima and maxima) in harmonic yields during molecular rotational revivals.
• * Correlating these timing features with specific values of rotational temperature and pump intensity.
• * Applying the method to nitrogen (N₂) molecules and subsequently to carbon dioxide (CO₂) molecules.

Main Results:

• * Demonstrated accurate simultaneous measurement of rotational temperature and pump intensity.
• * Showcased the method's sensitivity to these parameters through the analysis of harmonic signal timings.
• * Validated the technique's robustness by testing with various harmonic orders, gas pressures, and geometric configurations.

Conclusions:

• * The developed HHS-based method provides an accurate and reliable way to determine rotational temperature and pump intensity.
• * This technique enhances the precision of experiments involving laser-induced molecular alignment.
• * The method's versatility is confirmed by successful application to different molecular species like N₂ and CO₂.