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We used precision spectroscopy to analyze the R(53)24-1, P(49)24-1, and R(95)25-1 lines of molecular iodine ( 127 I 2 ) to establish optical frequency references for the laser cooling of Yb atoms using the 1 S 0 - 3 P 1 intercombination transition at 556 nm. A laser frequency instability of < 2 × 10 -12 (for 0.01 s < τ < 3000 s, τ is the average time of the measurement) was attained using the observed Doppler-free hyperfine transitions of the iodine lines. The absolute frequencies of the observed 63 hyperfine transitions were determined with an uncertainty of 7 kHz (fractional uncertainty of 1.3 × 10 -11 ). Highly accurate hyperfine constants were determined by fitting the measured hyperfine splittings to a four-term Hamiltonian that includes the electric quadrupole, spin-rotation, tensor spin-spin, and scalar spin-spin interactions with an uncertainty of approximately 1 kHz. The observed hyperfine transitions of molecular iodine provide new frequency references for research using atomic Yb, because these transitions are close to the intercombination transition of Yb at 556 nm.

Optical frequency combs play a crucial role supporting optical frequency standards and cover a wide range of wavelengths (octaves). However, broadening the comb spectrum to the short-wavelength visible region (λ < 500 nm), where GaN-based blue diode lasers are available, is not an easy task. In this study, we propose a method for measuring the laser frequency in the short-wavelength region using an intermediate laser and a noise-canceling scheme. We demonstrate this method by measuring the frequency of a GaN-based laser at 399 nm and confirming that the frequency measurement is not affected by the frequency noise of the intermediate laser.

Background: Congenital esophageal stenosis (CES) in adults is a rare disorder that can present as achalasia, particularly in the distal esophagus. We describe the salient features of CES in adults and identify the feasibility and short-term outcomes of peroral endoscopic myotomy (POEM) for CES., Methods: In this retrospective, single-center case series, we included 6 patients with a "misdiagnosis" of achalasia established elsewhere, ultimately diagnosed with CES and referred to our institution for POEM. Symptom improvement (clinical success rate), defined as an Eckardt Symptom Score (ESS) of <3 at 2-month follow up was assessed., Results: Six patients (median age: 40 [range: 18-58] years; 4 males) were included. A long-standing history of dysphagia, ring-shaped stenosis on endoscopic examination, "lopsided hourglass" sign on barium esophagogram, and high-resolution manometry findings indicated by a compartmentalized intrabolus pressure pattern with distinction between the stenotic area and the lower esophageal sphincter were the salient features identified. POEM could not be completed in the first 2 cases due to technical challenges. All subsequent 4 patients who underwent successful POEM, exhibited improved ESS of ≤3 (clinical success rate 100%) at 2 months post-POEM., Conclusions: Along with identification of salient features on several diagnostic modalities, a differential diagnosis of CES in adults must be considered in patients presenting with long-standing history of dysphagia arising from childhood and persisting into adulthood. Although favorable short-term outcomes of POEM were achieved, further evaluation is still warranted, and an inexperienced operator should not attempt POEM on CES patients due to its technical difficulties., Competing Interests: Conflict of Interest: Haruhiro Inoue is an advisor of Olympus Corporation and Top Corporation. He has also received educational grants from Olympus Corp., and Takeda Pharmaceutical Co. Anastasios Manolakis has received grant from the Hellenic Society of Gastroenterology and research fund from Janssen Pharma, (Copyright: © Hellenic Society of Gastroenterology.)