Use of (130)Te(2) for frequency referencing and active stabilisation of a violet extended cavity diode laser

High resolution spectroscopy of B0u+←X0g+ transitions in 130Te2: Reference lines spanning the 443.2-451.4 nm region

Molecular tellurium (130Te2) has long been regarded as a promising candidate for a variety of spectroscopic applications, especially as a frequency reference. Absorption lines of 130Te2 were published extensively in the past few decades, however, the spectral resolution was not sufficiently high to be considered a precision spectroscopic reference. Here, a high resolution spectral atlas of 130Te2 Doppler-free saturated absorption transitions is reported, and used to assign multiple ro-vibrational bands in the B(Σu-3)0u+←X(Σu-3)0g+ electronic transition via the Dunham model, giving updated Dunham parameters and diatomic constants for the B(Σu-3)0u+ state at an unprecedented level of precision. Our findings reveal spectroscopic properties of 130Te2 that might eventually contribute to frequency reference in precision measurement such as the quest for non-zero electron's Electric Dipole Moment (eEDM).

High resolution spectroscopic measurement of 130Te2: Reference lines near 444.4 nm for eEDM experiment using PbF molecules

Molecular tellurium (Te₂) offers a wide range of potential applications, including frequency reference. Spectroscopic results about the ¹³⁰Te₂ spectrum were previously reported, but few lines lie around the PbF transition of A (²Σ⁺) (υ' = 0) ← X₁²Π_1/2 (υ = 0) (∼444.4 nm) which is regarded as an eEDM (electron's Electric Dipole Moment) sensitive transition. Here electronic transition lines for ¹³⁰Te₂ were determined using the Saturated Absorption Spectroscopy method, where the origin of the transition band was investigated for the B₁ (³Σ_u^-)0_u⁺ (υ' = 10) ← X₁ (³Σ_g^-)0_g⁺ (υ = 5) transition. The Dunham model with high orders was utilized to assign these transition lines, while Dunham parameters of the excited state B₁ (υ' = 10) were updated to a new level. The Toptica TA-SHG Pro laser was then locked to a single absorption line using a P-I servo. Our results here not only provide the assigned atlas of Te₂ spectrum near 444.4 nm, but also contribute to a stable and sensitive spectroscopic detection of PbF molecules toward the eEDM measurement, which is significant in understanding the fundamental physics beyond the Standard Model.

High resolution spectroscopy on Te2: New lines for reference

Ro-vibrational spectra of different electronic states of molecules are often used as absolute wavelength or frequency standards. These standards are also used to mitigate any slow drift of laser frequency during an experiment. In the precision experiment, the two most commonly used molecular standards are iodine and tellurium, both are homo-nuclear diatomic molecules. The former is mostly used as standard for the long wavelength (600-900 nm) region, while the tellurium spectrum is widely used in short wavelength (400-550 nm) including near ultraviolet. A comprehensive data on tellurium spectra can be obtained from the tellurium atlas [1]. However near the 455 nm range where a number of important atomic resonance line, the atlas provides no significant data. We have performed high resolution modulation transfer spectroscopy (MTS) on tellurium molecule in a hot cell in the region close to 455 nm wavelength thereby obtained more than 100 new spectral lines which were not observed before. The linewidth of each of these peaks is about a few tens of MHz, making them suitable for laser frequency locking.

Diode Laser Induced Fluorescence for Gas-Phase Diagnostics

We highlight the capabilities and potential of diode laser induced fluorescence for measurements in gas-phase reacting flows. Many applications of diode lasers in practical sensing are based on absorption spectroscopy. Fluorescence-based diagnostics possess similar advantages in terms of practicality and implementation-cost but additionally are capable of achieving excellent spatial resolution. Diode laser fluorescence instruments have been employed for high-sensitivity trace gas monitoring in applications ranging from plasma physics to atmospheric chemistry. This article begins by describing the UV-visible diode laser technology used to perform fluorescence. The principles of diode laser induced fluorescence are then reviewed and a comparison is made with absorption spectroscopy. Examples are given of concentration measurements of both atomic and molecular trace gases. Recent work on using diode laser induced atomic fluorescence for precision measurements of flame temperature is also reviewed. We conclude by a discussion of future opportunities for diode laser fluorescence spectroscopy drawing attention to interesting potential target species as well as novel application areas, such as monitoring of synthesis processes for nanomaterials.