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Photoelectron imaging on vibrational excitation and Rydberg intermediate states in multi-photon ionization process of NH3 molecule.
- Source :
- Chinese Physics B; Aug2020, Vol. 29 Issue 9, p1-7, 7p
- Publication Year :
- 2020
-
Abstract
- The ionization processes of NH<subscript>3</subscript> molecule are studied by photoelectron velocity map imaging technique in a linearly polarized 400-nm femtosecond laser field. The two-dimensional photoelectron images from ammonia molecules under different laser intensities are obtained. In the slow electron region, the values of kinetic energy of photoelectrons corresponding to peaks 1, 2, 3, and 4 are 0.27, 0.86, 1.16, and 1.6 eV, respectively. With both the kinetic energy and angular distribution of photoelectrons from NH<subscript>3</subscript> molecules, we can confirm that the two-photon excited intermediate Rydberg state is A<superscript>∼1</superscript> () state for photoelectron peaks 2, 3, 4, and the three peaks are marked as 1<superscript>2</superscript>2<superscript>3</superscript> (2 + 2), 1<superscript>1</superscript>2<superscript>3</superscript> (2 + 2), and 1<superscript>0</superscript>2<superscript>3</superscript> (2 + 2) multi-photon processes, respectively. Then, peak 1 is found by adding a hexapole between the source chamber and the detection chamber to realize the rotational state selection and beam focusing. Peak 1 is labeled as the 1<superscript>3</superscript>2<superscript>3</superscript> (3 + 1) multi-photon process through the intermediate Rydberg state. The phenomena of channel switching are found in the slow electron kinetic energy distributions. Our calculations and experimental results indicate that the stretching vibrational mode of ammonia molecules varies with channels, while the umbrella vibration does not. In addition, we consider and discuss the ac-Stark effect in a strong laser field. Peaks 5 and 6 are marked as (2 + 2 + 1) and (2 + 2 + 2) above threshold ionization processes in the fast electron region. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 16741056
- Volume :
- 29
- Issue :
- 9
- Database :
- Complementary Index
- Journal :
- Chinese Physics B
- Publication Type :
- Academic Journal
- Accession number :
- 146907474
- Full Text :
- https://doi.org/10.1088/1674-1056/ab9431