12 research outputs found
Precision Measurement of M1 Optical Clock Transition in Ni12+
Highly charged ions (HCIs) have drawn significant interest in quantum
metrology and in search for new physics. Among these, Ni12+ is considered as
one of the most promising candidates for the next generation of HCI optical
clocks, due to its two E1-forbidden transitions M1 and E2, which occur in the
visible spectral range. In this work, we used the Shanghai-Wuhan Electron Beam
Ion Trap to perform a high-precision measurement of the M1 transition
wavelength. Our approach involved an improved calibration scheme for the
spectra, utilizing auxiliary Ar+ lines for calibration and correction. Our
final measured result of the M1 transition wavelength demonstrates a five-fold
improvement in accuracy compared to our previous findings, reaching the
sub-picometer level accuracy. In combination with our rigorous atomic-structure
calculations to capture the electron correlations and relativistic effects, the
quantum electrodynamic (QED) corrections were extracted. Moreover, comparing
with an estimate of the one-electron QED contributions by using the GRASP2018
package, we found that the present experimental accuracy is high enough for
testing the higher-order QED corrections for such a complex system with four
electrons in the p subshell.Comment: 15 pages, 5 figure
Diurnal Evapotranspiration and Its Controlling Factors of Alpine Ecosystems during the Growing Season in Northeast Qinghai-Tibet Plateau
It is generally believed that evapotranspiration at night is too miniscule to be considered. Thus, few studies focus on the nocturnal evapotranspiration (ETN) in alpine region. In this study, based on the half-hour eddy and meteorological data of the growing season (from May to September) in 2019, we quantified the ETN of alpine desert (AD), alpine meadow (AM), alpine meadow steppe (AMS), and alpine steppe (AS) in the Qinghai Lake Basin and clarified the different response of evapotranspiration to climate variables in daytime and nighttime with the variation of elevation. The results show that: (1) ETN accounts for 9.88~15.08% of total daily evapotranspiration and is relatively higher in AMS (15.08%) and AD (12.13%); (2) in the daytime, net radiation (Rn), temperature difference (TD), vapor pressure difference (VPD), and soil moisture have remarkable influence on evapotranspiration, and Rn and VPD are more important at high altitudes, while TD is the main factor at low altitudes; (3) in the nighttime, VPD and wind speed (WS) control ETN at high altitudes, and TD and WS drive ETN at low altitudes. Our results are of great significance in understanding ETN in the alpine regions and provide reference for further improving in the evapotranspiration estimation model