Longsheng Ma

Optical heterodyne velocity modulation spectroscopy enhanced by a magnetic rotation effect

Abstract Velocity modulation spectroscopy for detecting weak absorption of molecular ions has been improved by optical heterodyne detection and a magnetic rotation effect.

Study on the (1, 2) and (2, 3) bands in the comet-tail system of 12C16O+ by optical heterodyne magnetic rotation enhanced velocity modulation spectroscopy

Optical heterodyne magnetic rotation enhanced velocity modulation spectroscopy was employed to observe the absorption spectra of the (1, 2) and (2, 3) bands of the comet-tail (A2 Πi—X2Σ+) system of CO+ in the visible region. A rotational analysis was performed to obtain more precise molecular constants for the four involved vibrational levels. Moreover, accurate RKR potentials and the Franck-Condon factors are given for these four vibronic levels. This calclulation reveals that v = 0, 5, 10 vibrational levels in the A state will be perturbed by the v = 10, 14, 18 levels in the × state, respectively, and the v = 9 level might be weakly perturbed by the v = 17 level.

Optical heterodyne–Stark modulation spectroscopy

Abstract A spectroscopic scheme, which combines the Stark modulation with the optical heterodyne detection technique, improves the detection sensitivity by a factor of about 30 over that of Stark modulation spectroscopy alone.

Electronic energy transfer between the high-lying states of Na2

Abstract The collisional energy-transfer process from the 2 1 Π g to the C 1 Π u state of Na 2 has been studied using two-photon excitation in the 630–650 nm range and fluorescence observation of the C 1 Π u →X 1 Σ + g band. The relative vibrational population distribution of the C 1 Π u state is similar to a Gaussian function centered on a particular vibrational level and with a narrow width. The fluorescence spectra have been calculated and are in agreement with experimental results.

Measurement of the absorption spectrum of H2O+ in the visible region

Together with the 74 lines belonging to (0,9,0)-(0,0,0) band, the high-resolution absorption spectrum of H2O+ Ã2A1 - X2B1 system was observed in the visible region of 16680–17300 cm−1 using optical heterodyne magnetic rotation enhanced velocity modulation spectroscopy for the first time, which verifies the high sensitivity and high signal to noise ratio (S/N) of this technique.

Stabilization of mini-Nd: YVO4 laser using I2 hyperfine transition

By using a diode-pumped Nd:YVO4 / KTP intracavity frequency-doubling mini-laser and frequency modulation optical heterodyne spectroscopy, we have obtained spectrum of127I2 hyperfine structure near 532 nm. The laser frequency is locked to hyperfine transitions of I2. The analysis of error servo signal demonstrates that the laser frequency stability can reach 10−12 at 1 second average time.

Optical heterodyne-Zeeman modulation magnetic rotation spectroscopic technique

Optical heterodyne detection using 500 MHz phase modulation was combined with the Zeeman modulation-magnetic rotation spectroscopy (ZM-MRS) to form a new spectroscopic technique, which effectively reduced the amplitude fluctuation from laser source and greatly improved the signal-to-noise ratio in the detection of transient molecules.