Direct Wavelength Measurement of the Visible M1 Transition in Ba⁷⁺with a Novel Calibration Method

Abstract

We observed and directly measured the M1 transition between the two states of the fine structure splitting in the ground state of Ba 7+ with a visible spectrometer coupled to a compact electron beam ion trap. To validate the measurement accuracy, we demonstrated a calibration method using Ar + emissions from buffer gas. The wavenumber in vacuum was determined to be 23591.57 (15) cm −1 .

Probing Multiple Electric Dipole Forbidden Optical Transitions in Highly Charged Nickel Ions

“…The total wavelength uncertainty of this observation and calibration scheme was approximately 2 pm, which was comparable to the uncertainty of the scheme that the measured lines were calibrated by the lines from the buffer gas observed by a similar resolution spectrograph [44,45], but larger than the uncertainty of the scheme that the calibration source was overlapped with the real image of the ion observed by a higher resolution spectrograph [42]. Compared to these two schemes, our scheme is more convenient and flexible.…”

Simultaneous observation of noble gases and highly charged ions in an electron beam ion trap for accurate wavelength calibration of optical transitions

“…Typical emission line intensities of Ne and Ar + increased linearly with the amount of injected buffer gas. The emission line around 423 nm was related to the M1 transition between fine-structures in the ground configuration of Ba 7+ , which we reported in the previous paper [17]. We assigned the emission line of Ba 8+ around 500 nm to the 3 P 1 -3 P 2 transitions in the first excited electron configuration [Kr]4d 10 5s5p by comparing its wavelength with the energy levels of Ba 8+ previously investigated by extreme ultraviolet(EUV) emission spectroscopy [30].…”

“…The experiments involved injecting elemental Ba, I, Ne, and Ar into CoBIT. Ba atoms were injected by evaporating the cathode material (BaO) of the electron gun [17,18]. The Ne and Ar gases were introduced into CoBIT as buffer gases using a gas injector through a variable leak valve.…”

“…Γ q = γ q ) for several HCIs with an M1 transition that prominently emits at visible and near-visible wavelengths. Our previous papers [17,18] reported the simultaneous observation of emission lines of Ba 7+ and Ar + , and of Ba 6+ and neutral Ne. We also simulutaneously observed a near-infrared emission line of I 8+ and reference lines of neutral Ne [22], although the spectrum was not previously presented.…”

“…The Freiberg and Heidelberg EBIT group succeeded in this simultaneous observation of the visible emission of Ar 13+ and the reference emission from Ar and Ar + by introducing a lot of Ar gas three times higher than usual [14][15][16]. Recently, we demonstrated a versatile calibration method for the visible and near-visible wavelength range using buffer noble gases different elements from objective HCIs [17,18]. This calibration method can be applied to various heavy HCIs, not only highly charged noble gas ions, and has since been adopted by the Shanghai EBIT group [19,20].…”