Cozijn F M J, Diouf M L, Ubachs W
Department of Physics and Astronomy, LaserLab, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
Phys Rev Lett. 2023 Aug 18;131(7):073001. doi: 10.1103/PhysRevLett.131.073001.
The saturated absorption spectrum of the hyperfineless S(0) quadrupole line in the (2-0) band of H_{2} is measured at λ=1189 nm, using the NICE-OHMS technique under cryogenic conditions (72 K). It is the first time that a Lamb dip of a molecular quadrupole transition has been recorded. At low (150-200 W) saturation powers a single narrow Lamb dip is observed, ruling out an underlying recoil doublet of 140 kHz. Studies of Doppler-detuned resonances show that the redshifted recoil component can be made visible for low pressures and powers, and prove that the narrow Lamb dip must be interpreted as the blue recoil component. A transition frequency of 252 016 361 164 (8) kHz is extracted, which is off by -2.6 (1.6) MHz from molecular quantum electrodynamical calculations therewith providing a challenge to theory.
在低温条件（72K）下，使用NICE - OHMS技术，在λ = 1189 nm处测量了H₂的（2 - 0）带中超精细无的S(0)四极线的饱和吸收光谱。这是首次记录到分子四极跃迁的兰姆凹陷。在低（150 - 200W）饱和功率下，观察到单个窄兰姆凹陷，排除了140kHz的潜在反冲双峰。对多普勒失谐共振的研究表明，对于低气压和低功率，红移的反冲分量可以变得可见，并证明窄兰姆凹陷必须解释为蓝移的反冲分量。提取出跃迁频率为252 016 361 164(8)kHz，与分子量子电动力学计算结果相差-2.6(1.6)MHz，这给理论带来了挑战。
