Calculation of parity-nonconserving optical rotation in iodine at 1315 nm

Abstract

We examine the feasibility of a parity non-conserving (PNC) optical rotation experiment for the 2 P 3/2 → 2 P 1/2 transition of atomic iodine at 1315 nm. The calculated E1PNC to M 1 amplitude ratio is R = 0.80(16) × 10 −8 . We show that very large PNC rotations (greater than 10 µrad) are obtained for iodine-atom column densities of ∼ 10 22 cm −2 , which can be produced by increasing the effective interaction pathlength by a factor of ∼ 10 4 with a high-finesse optical cavity. The simulated signals indicate that measurement of the nuclear anapole moment is feasible, and that a 1% PNC precision measurement should resolve the inconsistency between previous measurements in Cs and Tl. [5][6][7][8]. The highlight of these efforts was the 0.35% precision measurement of nuclear-spin-independent PNC in Cs, and the 14% precision measurement of the nuclear spin-dependent PNC for the odd-proton nucleus of 133 Cs [4]. However, measurement of the anapole moment in Cs disagrees with Tl [4,5], and also with some theoretical nuclear calculations ([9-11] and references therein). To help resolve these inconsistencies, and to improve the atomic PNC tests of the standard model, further experiments are needed. For example, there is a proposal to measure the nuclear anapole moment using the PNC-generated hyperfine frequency shift of dressed states in atoms [12], with particular proposals for Cs [13] and Fr [14]. However, for other PNC candidates, as the precision in the atomic theory is not expected to significantly surpass the current experimental or theoretical PNC precision of Cs, future PNC experiments have focused on other fruitful directions, such as the measurement of atomic PNC on a chain of isotopes [9,15], or the measurement of nuclear anapole moments. Therefore, along these lines, PNC experiments are in progress on Yb and Dy at Berkeley [16,17], on Rb and Fr at the Tri-University Meson Facility (TRIUMF, University of British Columbia) [18,19], on Ra + at KVI Groningen [20], and on Ba + at the University of Washington, Seattle [21]. Recently, Bougas et al.

High steady-state column density of I(2P3/2) atoms from I2 photodissociation at 532 nm: Towards parity non-conservation measurements

“…We assume that the population of excited states of I 2 and production of I 3 molecules are negligible (such assumptions have been used in previous studies to determine the rate constant k r for the recombination of iodine atoms 16 17 ). In this case, the rate equation governing the production rate of atomic iodine from photodissociating I 2 is given by 10 17 :…”

“…50–200 W commercial lasers are available), and by improving the cell coatings further. Increased photodissociation will also reduce the Lorentz width of the 1315 nm transition, which is beneficial for polarimetry applications 10 : indeed, collisional broadening by I 2 is about 2 π × 7.7 (Mrad/s)/mbar, and by I about 2 π × 3.2 (Mrad/s)/mbar 26 . At our current I 2 pressure of ~0.2 mbar, the Lorentz linewidth is ~2 π × 1.5 Mrad/s.…”

“…The operation of the cavity has been demonstrated through the measurement of chiral optical rotation of gases, liquids, and thin films 12 13 . This signal enhancement, and the background suppression and subtraction procedures, open the way for PNC optical rotation measurements in other atomic and molecular systems, which have smaller values of R and/or can be produced at smaller column densities, such as I( 2 P 3/2 ) 10 and metastable Hg and Xe 11 , molecular oxygen 14 , and other diatomic molecules 15 . For example, for the I( 2 P 3/2 ) → I( 2 P 1/2 ) M1 transition at 1315 nm, R = 0.8 × 10 −8 , which is about 20 times smaller than that of the Tl( 2 P 1/2 ) → Tl( 2 P 3/2 ) M1 transition at 1.28 μ m: R = 1.5 × 10 −7 .…”

“…Recently, our group has proposed a method for the measurement of parity nonconserving (PNC) optical rotation using a novel bowtie cavity 9 10 11 to enhance the effective column density by the number of cavity passes (~1000), while also introducing signal reversals which allow the isolation of the PNC signals from backgrounds. The operation of the cavity has been demonstrated through the measurement of chiral optical rotation of gases, liquids, and thin films 12 13 .…”

“…However, Katsoprinakis et al . 10 proposed to compensate for this smaller value of R by using large cavity-enhanced pathlengths (~1000 m) to achieve column densities of about 10 20 cm −2 and higher, but also by generating the I( 2 P 3/2 ) atoms from the photodissociation of I 2 molecules using 532 nm laser light, at low pressure and near room temperature, so that the Lorentz and Doppler widths can be significantly reduced, to ~2 π × 1 Mrad/s and ~2 π × 150 Mrad/s, respectively. In addition, the production of high-density atoms through photodissociation at room temperature is more convenient and more compatible with an optical cavity experiment than using a high-temperature oven.…”