Laser induced fluorescence and radiative lifetimes of the low-lying electronic states of gaseous AgF

Abstract

At the fringes of the visible region, two low-lying 1 (Ω=1) electronic states A′Ω1 and aΩ1 of gaseous AgF located ∼4300 cm−1 below the previously known lowest excited A0+ state have been excited for the first time in a silver vapor–fluorine reaction system. The A′Ω1–X 1Σ+ and a Ω1–X 1Σ+ band systems (also observed in chemiluminescence) have been excited and studied using pulsed laser induced fluorescence spectroscopy. The band system associated with the A′Ω1–X 1Σ+ transition has been rotationally analyzed. The UV fluorescence of the A0+ and B0+–X 1Σ+ transitions has also been excited. The radiative lifetimes of these four low-lying electronic states have been measured as 7.1 μs (A′Ω1), 9.1 μs (aΩ1), 240 ns (A0+), and 21 ns (B0+), respectively, revealing that the two Ω=1 states are of triplet character, while the two 0+ states are of singlet character. The observed low-lying states of AgF appear to dissociate adiabatically to neutral atoms in contrast to the apparent dissociation of the low-lying electronic states in CuF to ion pairs. The observation of the low-lying 1 states of AgF also indicates the existence of similar stable 1 states for the remaining silver halides, all of which should absorb visible photons. Major molecular constants of the newly observed A′Ω1 state of 107AgF are Te=24 950.71(10) cm−1, ΔG1/2=506.74(8) cm−1, Be=0.281 32(15) cm−1, De=0.116(60)×10−6 cm−1, and re=1.927 Å.