# First-principles insights into ultrashort laser spectroscopy of molecular nitrogen

## TL;DR

This study uses time-dependent density functional theory to analyze how ultrashort laser pulses influence photoelectron emission from nitrogen molecules, revealing the effects of pulse parameters and molecular orientation on electron spectra.

## Contribution

It provides new insights into the control of photoelectron characteristics through laser pulse parameters and molecular orientation in nitrogen spectroscopy.

## Key findings

- Molecular orientation significantly affects photoelectron orbital character.
- Laser pulse duration influences orbital resolution and photoelectron intensity.
- Threshold for two-photon absorption in nitrogen is theoretically determined.

## Abstract

In this research, we employ accurate time-dependent density functional calculations for ultrashort laser spectroscopy of nitrogen molecule. Laser pulses with different frequencies, intensities, and durations are applied to the molecule and the resulting photoelectron spectra are analyzed. It is argued that relative orientation of the molecule in the laser pulse significantly influence the orbital character of the emitted photoelectrons. Moreover, the duration of the laser pulse is also found to be very effective in controlling the orbital resolution and intensity of photoelectrons. Angular resolved distribution of photoelectrons are computed at different pulse frequencies and recording times. By exponential growth of the laser pulse intensity, the theoretical threshold of two photons absorption in nitrogen molecule is determined.