Direct measurement of the fine-structure interval and gJ factors of singly ionized atomic carbon by laser magnetic resonance

Abstract

We present the results of laser magnetic resonance measurements performed on the ground 2 P state of singly ionized atomic carbon (C II). The 2 P 312 +-2 P 112 fine-structure intervals of both 12~+ and 13 C+ ha~e been determined with a precision of approximately 1 ppm, and the gJ factors to approXImately one part m 10 4 • Specifically, we find that gJ= 1 ; 2 = 0.66576(11) and gJ= 3; 2 = 1.33412(11), while for 12 C+ !lEoeP3!2 +-2 P1;2) = 1900536.9(1.3) MHz, with !lE 0 eP 312 +-2 Pl/ 2) = 1900545.8(2.1) and !lEeP312 +-2 P~/2• F= 2 ~ 1) = 1900466.1(2.3) MHz in 13 C+. The highly precise values of the 12 C II and 13 C II fine-structure mtervals venfy the already secure far-infrared astronomical identification of C + and should allow the interstellar 12 C / 13 C ratio to be unambiguously determined in a number of environments.

Spectrally resolved C II emission in M 33 (HerM33es)

“…5). This transition, F = 2 → 1, is expected to be the strongest of the three hyperfine transitions (Cooksy et al 1986). Although the velocity coverage of the spectra includes the two other components, they are not detected.…”

“…The three hyperfine components of the [ 13 C ii] line have frequencies equivalent to offsets of −66, +11, and +63 km s −1 , respectively, from the [ 12 C ii] line center at 1 900 536.9 ± 1.3 MHz (Cooksy et al 1986;Stacey et al 1991;Boreiko & Betz 1996). The ratio of the sum of the three hyperfine [ 13 C ii] transitions to the [ 12 C ii] line intensity, coupled with the relative abundance ratio, provides a measure of the optical depth of the [ 12 C ii] emission (e.g.…”

“…This region is likely to be more massive and extended in sub solar-metallicity galaxies and may represent a significant but hitherto unmeasured gas mass. Hyper-fine components of the [ 13 C ii] line bracket the main isotope (Cooksy et al 1986) and with HIFI we are, in principle, able to separate the lines allowing a direct determination of the optical depth.…”

TheHerschelM 33 extended survey (HerM33es): PACS spectroscopy of the star-forming region BCLMP 302

“…The HIFI spectrum was taken on 01 August 2010 during one hour of observing time using the load chop mode with the same reference position as used for the PACS observation. The frequency of the [C ii] line is 1 900 536.9 MHz, known to within an uncertainty of 1.3 MHz (0.2 km s −1 ) (Cooksy et al 1986). The blue-shifted line required the local oscillator to be tuned to 1899.268 GHz, about the highest frequency accessible to HIFI.…”

Atomic data for IR and sub-mm wavelengths

“…Although wavelengths of a few lines have been directly measured using laser spectroscopy (e.g. Cooksy, Blake, & Saykally 1986), or by analysis of astronomical spectra (e.g. Feuchtgruber, Lutz & Beintema 2001), accurate wavelengths for these lines are usually determined from optimized energy levels.…”