Time-resolved double-resonance spectroscopy: Lifetime measurement of the 6 1Σg+(7,31) electronic state of molecular sodium

Abstract

We report on the lifetime measurement of the 6 1Σg+(7,31) state of Na2 molecules, produced in a heat-pipe oven, using a time-resolved spectroscopic technique. The 6 1Σg+(7,31) level was populated by two-step two-color double resonance excitation via the intermediate A 1Σu+(8,30) state. The excitation scheme was done using two synchronized pulsed dye lasers pumped by a Nd:YAG laser operating at the second harmonics. The fluorescence emitted upon decay to the final state was measured using a time-correlated photon counting technique, as a function of argon pressure. From this, the radiative lifetime was extracted by extrapolating the plot to collision-free zero pressure. We also report the calculated radiative lifetimes of the Na2 6 1Σg+ ro-vibrational levels in the range of v = 0–200 with J = 1 and J = 31 using the LEVEL program for bound-bound and the BCONT program for bound-free transitions. Our calculations reveal the importance of the bound-free transitions on the lifetime calculations and a large difference of about a factor of three between the J = 1 and J = 31 for the v = 40 and v = 100, respectively, due to the wavefunction alternating between having predominantly inner and outer well amplitude.

Rovibrationally resolved radiative lifetime and collisional cross section measurements of the 61Σg+(v=6,Wagle1, Pant2, Converse3 et al. 2021Journal of Quantitative Spectroscopy and Radiative TransferSelf Cite0000View full textAdd to dashboardCite

“…The measured collisional cross sections for the v=6, 7, and 8 quantum states are found to be in excellent agreement within the error limits. The measured radiative lifetimes of Na 2 6 1 Σ + g (v=8,J=31) and 6 1 Σ + g (v=6,J=31) (even vibrational states) are in excellent agreement with each other but both are smaller compared to the 6 1 Σ + g (v=7,J=31) (odd vibrational state) [12]. Similar lifetime variations in the Na 2 4 1 Σ + g state were reported [14].…”

“…2. The details of the setup were explained in our previous work [12], hence it will not be presented here. We used a four-armed heatpipe oven to heat sodium metal at desired temperature and pressure.…”

Time-Resolved Vibrational Spectroscopy to Measure Lifetime of the E$^3Π_g(v=3)$ state of Molecular Iodine

“…On the other hand, measurements of a long sequence of lifetimes as a function of (v, J) can reveal scaling laws in these quantities. Recently published articles reported a strong dependence of molecular lifetime on rovibrational level's wavefunctions [33,34]. This work will be followed by making series of lifetime measurements as a function of vibrational or rotational quantum numbers in diatomic molecules.…”

“…This is specifically important because the E-state correlates diabatically with the ground state I − ( 1 S o )+I + ( 3 P 2 ) of the separated ions and diabatic dissociation limit corresponds to about 72000 cm −1 [32]. Recently, calculated radiative lifetimes for the alkali dimer ion pair states have revealed strong variations as a function of internuclear distance because of the effect of the ion pair potentials [28,33,34].…”

Experimental investigations on rotation–vibration energy transfer in H2–N2 collisions

“…Saaranen et al [15] used time-resolved double resonance spectroscopy to experimentally and theoretically study the lifetime of the 6 1 Σ + g (7,31) state of sodium molecules. The Na 2 6 1 Σ + g (7,31) state was excited via the laser doubleresonance method, and the experimental life of the trap was measured.…”