All-optical triple resonance spectroscopy of Na2 and scheme for state-selective formation of highly rotationally-excited diatomic molecules

Authors

Jing Li, University of Connecticut

Date of Completion

January 2000

Keywords

Physics, Molecular|Physics, Atomic|Physics, Optics

Degree

Ph.D.

Abstract

This investigation focuses on the spectroscopic study of the fundamental question: “how to control and manipulate molecules”. The following three studies touch these questions from different angles. ^ First in Chapter 2, we use the powerful AOTR to probe Na₂ molecules near their equilibrium intemuclear distance, R_e ^″(∼3Å), but at high levels of electronic excitation. For the nf(l = 3) series of Na₂, quantum defects are calculated from theoretical values of the core quadrupole moment and polarizabilities. We predict the stroboscopic effect should first occur when n = 52 for the nf series, as we observe, rather than at n = 69 for the np series. Our data thus confirm that the strongest series is the nf. Hence the ionization potential is not 39478.75 ± 0.04 cm⁻¹ as previously reported, but rather 39478.101 ± 0.013 cm⁻¹, implying a molecular ion dissociation energy of D₀⁰(Na ₂⁺) = 7914.038 ± 0.014 cm⁻¹. ^ Then in Chapter 3, we again use AOTR to shift the distance probed to ∼6.44Å, but again explore high levels of electronic excitation. We have observed the 5¹Π_u, 6¹Σ_u ⁺ and 7¹Σ_u⁺ states of Na₂. Although the absolute vibrational numbering is uncertain, the rotational constants are obtained. The Franck-Condon window concept is presented with calculated Franck-Condon factors based on the theoretical 5 ¹Π_u, 6¹Σ_u⁺ and 7¹Σ_u⁺ potential energy curves of Magnier. Finally in Chapter 4, the molecules again remain at relatively short distance near R_e^″, but a scheme is proposed for making highly rotationally excited diatomic molecules (“Super Rotors”) in their ground vibrational and electronic state, e.g. ⁶Li ₂ X ¹Σ_g⁺ (v = 0, J ≥ 115) where the rotational energy exceeds the bond strength (E(0,J)-E(0,0) ≥ D₀⁰). Such levels, while strictly speaking quasibound, have very long tunneling lifetimes, and should have very interesting and unique collisional properties, especially at low temperature. The rotation of the molecules is “spun up” by sequential irradiation by R branch photons in the A ¹Σ_u⁺–X ¹Σ_g⁺ bands starting with cold molecules at low J. Spontaneous emission to other vibrational levels is overcome by using a pump laser and its multiple Raman sidebands as in previous work on “spinning down” diatomics. ^

Recommended Citation

Li, Jing, "All-optical triple resonance spectroscopy of Na2 and scheme for state-selective formation of highly rotationally-excited diatomic molecules" (2000). Doctoral Dissertations. AAI9969079.
https://digitalcommons.lib.uconn.edu/dissertations/AAI9969079