Characterisation of the electronic ground states of BaH+ and BaD+ by high-resolution photoelectron spectroscopy

IF 2.9 3区化学 Q3 CHEMISTRY, PHYSICAL Physical Chemistry Chemical Physics Pub Date : 2024-12-03 DOI:10.1039/D4CP04323E

J. R. Schmitz and F. Merkt

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Abstract

The rovibrational energy-level structures of BaH⁺ and BaD⁺ in their X^{+ 1}Σ⁺ electronic ground state have been characterised by pulsed-field-ionisation zero-kinetic-energy photoelectron spectroscopy following resonance-enhanced (1 + 1′) two-photon excitation from the BaH/BaD X ²Σ⁺ ground state via the E ²Π_1/2 (v′ = 0, 1) intermediate levels. A full set of rovibrational molecular constants for the BaH⁺ and BaD⁺ ground states has been derived for the first time and the adiabatic ionisation energies of BaH and BaD were determined to be 38 679.96(20) and 38 652.69(20) cm⁻¹, respectively. Photoelectron spectra recorded via E-state levels of selected rovibronic parity exhibit pronounced intensity alternations of transitions to rotational states of the cations with even- and odd-valued rotational-angular-momentum quantum number N⁺. This observation is interpreted by invoking dominant contributions of even- photoelectron partial waves in the photoionisation of the E ²Π_1/2 (v′ = 0, 1) intermediate states of barium hydride. The lowest pure-rotational transition frequencies of BaH⁺ and BaD⁺ are derived from the photoelectron spectra which may help the detection of BaH⁺ in the microwave and millimetre-wave ranges.

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用高分辨率光电子能谱表征BaH$^{+}$和BaD$^{+}$的电子基态

BaH/BaD X $^2\Sigma^+$基态经E $^2\Pi_{1/2}(v=0,1)$中间能级共振增强（$1+1^\prime$）双光子激发后，BaH $^+$和BaD $^+$在X $^+$$^1\Sigma^+$电子基态的旋转振动能级结构用脉冲场电离零动能光电子能谱进行了表征。首次导出了BaH $^+$和BaD $^+$基态的全套旋转振动分子常数，确定了BaH和BaD的绝热电离能分别为38679.96（20）和38652.69(20)cm $^{-1}$。通过选择的滚振宇称的e态水平记录的光电子能谱显示出具有偶数和奇值旋转角动量量子数$N^+$的阳离子向旋转态转变的明显强度变化。这一观察结果是通过引用在氢化钡E $^2\Pi_{1/2}(v=0,1)$中间态的光电离中偶$\ell$光电子偏波的主要贡献来解释的。从光电子能谱中得到了BaH $^+$和BaD $^+$的最低纯旋转跃迁频率，这有助于在微波和毫米波范围内检测BaH $^+$。

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来源期刊

Physical Chemistry Chemical Physics 化学-物理：原子、分子和化学物理

CiteScore

5.50

自引率

9.10%

发文量

2675

审稿时长

2.0 months

期刊介绍： Physical Chemistry Chemical Physics (PCCP) is an international journal co-owned by 19 physical chemistry and physics societies from around the world. This journal publishes original, cutting-edge research in physical chemistry, chemical physics and biophysical chemistry. To be suitable for publication in PCCP, articles must include significant innovation and/or insight into physical chemistry; this is the most important criterion that reviewers and Editors will judge against when evaluating submissions. The journal has a broad scope and welcomes contributions spanning experiment, theory, computation and data science. Topical coverage includes spectroscopy, dynamics, kinetics, statistical mechanics, thermodynamics, electrochemistry, catalysis, surface science, quantum mechanics, quantum computing and machine learning. Interdisciplinary research areas such as polymers and soft matter, materials, nanoscience, energy, surfaces/interfaces, and biophysical chemistry are welcomed if they demonstrate significant innovation and/or insight into physical chemistry. Joined experimental/theoretical studies are particularly appreciated when complementary and based on up-to-date approaches.