光周波数コムを利用したナフタレンの高分解能レーザー分光

抄録

In high-resolution molecular spectroscopy, precise measurements of the optical frequency are crucial to evaluate minute shifts and splittings of the energy levels. In this study, we developed a frequency measurement system of cw lasers scanning the wide range employing an optical frequency comb. We demonstrated the frequency measurement of a scanning dye laser, and analyzed the spectral characteristics during the laser scan. The developed system was applied to Doppler-free two-photon absorption spectroscopy of S1 1B1u(v4 = 1)←S0 1Ag(v = 0) transition of naphthalene. We obtained wellresolved rovibronic spectra with the linewidth of 2.48 MHz, and determined absolute frequencies with the uncertainty of several tens of kHz. For the Q(K)Q(J) transitions, the rotational lines were assigned, and molecular constants in the excited state were determined.