Frequency Stabilization of CH₃OH Laser at 469 µm to Millimeter-Wave Frequency Standard

Abstract

It has recently been shown that the statistical mechanics of crystal melting maps to A-model topological string amplitudes on non-compact Calabi-Yau spaces. In this note we establish a one to one correspondence between two and three dimensional crystal melting configurations and certain BPS black holes given by branes wrapping collapsed cycles on the orbifolds C 2 /Z n and C 3 /Z n × Z n in the large n limit. The ranks of gauge groups in the associated gauged quiver quantum mechanics determine the profiles of crystal melting configurations and the process of melting maps to flop transitions which leave the background Calabi-Yau invariant. We explain the connection between these two realizations of crystal melting and speculate on the underlying physical meaning.

Frequencies of Optically Pumped Sub-Doppler Far-Infrared Laser Lines of Methanol

“…In previous works, the frequency resettability was limited by the locking of the FIR laser line to the top of the Doppler-broadened gain curve (2,3). Our recent measurements have improved the frequency accuracy by about a factor of 20 and make them much more accurate frequency and wavelength sources for spectroscopic applications.…”

“…Table 1 summarizes the frequency measured using 1F detection for the line at 570 m and 3F for the other lines. The total frequency uncertainty calculated from expression [2] is 27 kHz. Table 2 compares our more accurate results with frequencies using tunable radiation in the FIR region (TuFIR) for absorption measurements in the excited vibrational state of methanol and with laser radiation.…”