A²Π_u and 1⁴Σ_u^– States of Br₂⁺ Studied by [1+1] Two-Photon Dissociation Spectroscopy in a Cold Ion Beam

Abstract

The A2Πu–X2Πg and 14Σu ––X2Πg electronic transition spectra of Br2 + have been studied in the 500–720 nm wavelength range in a cold ion beam using a cryogenic cylindrical ion trap velocity map imaging spectrometer. The cryogenic ion trap produces a rotationally and vibrationally cold mass selected ion beam of Br2 +, which simplifies the experimental spectra from vibrational hot bands and bands of mixed isotopic species. Vibrationally resolved photofragment excitation spectra are recorded for individual isotopologues of Br2 + (79Br2 +, 79Br81Br+, 81Br2 +) by [1+1] two-photon dissociation spectroscopy. Velocity map imaging of the photofragmented Br+ ions provides complementary information in the determination of spin–orbit states involved in corresponding electronic transitions. An experimental identification of the 14Σu – state has becomes possible based on the present experimental results and previously reported theoretical calculations. Vibrational analyses of the photofragment excitation spectra have yielded spectroscopic parameters, including state origins, harmonic frequencies, and anharmonic constants, for both A2Πu and 14Σu – states. The observed A2Πu state spin–orbit splitting and the “spin-forbidden” 14Σu ––X2Πg transition band intensities indicate considerable spin–orbit couplings between the 14Σu – and A2Πu states. In addition, two groups of weak vibrational bands are also observed in the experimental spectra of 79Br81Br+, which may be due to symmetry-forbidden transitions from the X2Πg ground state to low-lying gerade states.

Probing the Charge-Transfer Potential Energy Surfaces by the Photodissociation of [Ar–N2]+

“…In the present study, we report an experimental study on the photodissociation dynamics of the [Ar–N 2 ] + cations by using a newly constructed cryogenic cylindrical ion trap velocity map imaging (CIT-VMI) instrument. , The high-resolution recoiling velocity images of photofragments have allowed us to determine the vibrational state distributions of the charge-transfer-associated product channels. , The experimental results illustrate the vibrational state correlation between the ionic N 2 + and neutral N 2 photofragments and allow us to probe the charge-transfer dynamics on the underlying vibronic PESs (Figure ).…”

Photodissociation Dynamics of the [O2–H2O]+ Ionic Complex

“…Based on the energy conservation rule in a photodissociation reaction, we have where E INT ([O 2 –H 2 O] + ) is the initial internal energy of the parent [O 2 –H 2 O] + , E h ν the photoexcitation energy, D 0 the dissociation energy of the ground state [O 2 –H 2 O] + to a specific product channel, E INT the total internal energy of photofragments, and E avl the total energy available to be partitioned between E TKER and E INT . Similar to our previous studies by the same instrument, ,− the parent ions could be efficiently cooled down to electronically and vibrationally ground state in the cold ion trap, i.e., the term is negligible. For the studied [O 2 –H 2 O] + system, the dissociation energy D 0 correlated with the lowest dissociation limit, i.e., channel (), has been discussed by a number of researchers, − ,, but an accurate determination from experiments is still lacking.…”

Attosecond XUV probing of vibronic quantum superpositions in Br$_2^+$

“…1d). The experimentally known harmonic frequencies are 205.0, 160.8, 200.6, and 197.8 cm −1 for the 2 Π 3/2,u , 2 Π 1/2,u , 4 Σ 3/2,u , and 4 Σ 1/2,u states, respectively [29]. The deviations between the measured and reference harmonic frequencies implicate a vibrational anharmonicity and a significant manifold of higher vibrational states excited among these electronic states.…”

“…Here, we present an attosecond transient absorption study on coherent electronic-vibrational dynamics of ionic molecular bromine (Br + 2 ). This species has several bound electronic states in the valence levels [27][28][29], and thus offers an ideal platform to study vibronic superpositions. Also, no intramolecular vibrational redistribution can occur in diatomic molecules, and the effects of vibra- π-π* tional dephasing and recurrences on electronic superpositions can be interpreted explicitly.…”